It probably goes without saying that potato aficionados are a breed unto themselves, especially when it comes to seeking out the most exotic varieties of spuds.
Then again, there are potatoes, and there are potatoes. Anyone who grows heirloom potatoes knows firsthand that the flavor of these wonderful old-time tubers is as varied and complex as any common fruit—apples and grapes for example, and if there is a potato Olympus somewhere in the high Andes of South America, then certainly the Yema de Huevo (“egg yolk”) potato and the Papa Chaco (“clay potato”) potato belong among that halcyon few. Hands down, these two varieties are among the most sought after and highly valued by connoisseurs of South American cookery not only for their unique color and flavor, but also because they have so easily adapted themselves to the classic national cuisines of high-altitude kitchens from Colombia to Peru.
Egg Yolk Potato
First, let’s talk about the Yema de Huevo. Perfectly round with brilliant saffron yellow skin and flesh, these potatoes are also about the same diameter as an egg yolk, hence the name in Spanish. In the native Quechua language of Peru it is called chaucha. And as you might imagine, with such an intense color, the potato is very rich in carotenoids, a nutritional plus that has made it almost iconic among vegetarians and health-food enthusiasts in South America. Unfortunately, this rare potato has not been available in the United States until quite recently.
The good news is that growers in different parts of the country are presently giving it a trial to see how well it does in our northern latitudes, since many Andean potatoes are sensitive to day length. This sensitivity is due to the fact that in their native homelands, they are planted in regions close to the equator, and while the potatoes may be growing in high-altitude microclimates where cool, moist weather is the norm, day and night are about equal, and this affects tuberization.
I have experienced this affect firsthand: After planting Peruanita, a Peruvian potato of Inca origin, it literally melted in the ground. My Pennsylvania soil was too warm too soon and the sunlight too intense (I am on the same latitude as Madrid, Spain). Getting potatoes to acclimate to these differences can require many years of selective breeding. Fortunately, that work was already done for us with Yema de Huevo.
I received my egg yolk potatoes in April 2013 as part of the USDA Agricultural Research station’s Potato Introduction Project organized out of the potato headquarters at Sturgeon Bay, Wisconsin. Because the USDA wanted samples of my White Elephant and Snowflake heirloom potatoes for the national collection, I was able to arrange a trade for the Yema de Huevo. If the truth be told, I had been looking for this Andean potato for many years and had seen it illustrated in cookbooks I had collected from South America, thus long at last my quest was realized. The USDA had acquired samples of the potato in Boyaca, Colombia, and then after isolating it to make sure it was free of diseases, created what I call “test tube” baby potatoes for those of us involved in the introduction project.
What this means is that botanists at the USDA took genetic material from the original imported potatoes and created marble-sized test tube samples, which were then sent to us to plant. I had heard about this process, which is both time consuming and expensive, yet extremely good for creating “genetically clean” seed stock. Just the same, this was my first experience planting them. Initially, you wonder how any large, healthy potato plant could ever emerge from such tiny nuggets of life, but the results were spectacular, in part I suspect because we had a cool rainy spring in Pennsylvania which arrived at the right time for the potatoes. But just to err on the side of caution, I also started the potatoes in large pots in my greenhouse, so they were up and growing vigorously when I finally moved them outside.
For the scientific minded, the USDA potato accession number for Yema de Huevo is PI 665487, thus its technical details can be researched via GRIN, the USDA online database. What makes this potato even more unusual is that it belongs to a totally different species from the common potatoes we buy at the supermarket (Solanum tuberosum). There are more than 5,000 varieties of potatoes spread over eight or nine species (the exact taxonomy is still under debate), and many of these species were domesticated in South America independently in different locations.
Botanically speaking, Yema de Huevo is the product of one of those independent domestications and it is classified as Solanum phureja, subspecies phureja. This means that it is a diploid species with 24 chromosomes as opposed to the 48 found in common potatoes. How this less-complex genetic structure relates to nutrition is one question that has not been answered (although worth pursuing). Anecdotally, South Americans will say that the potato is easier to digest or acts in the gut like roughage, which may seem at first glance contradictory, but these observations may stem from the way the potato is prepared. In Colombia and Ecuador it is often deep-fried whole and eaten as a snack; it is also added whole to soups and stews. It is so yellow that when steamed, it will also color the cooking water. When poached with carrots, it will make them change to a brighter shade of orange.
For the home gardener there are a few pointers to keep in mind. The vines for this potato are tall (about 28 inches), but large-leaved and rather floppy, so they should be hilled up as high as possible. The young plants also exhibit a yellowish tinge in the new leaves, although this coloration gradually disappears as the plants mature. Most surprising are the flowers, which bloom in masses of six or eight and literally cover the top parts of the plants. They are vibrant rose and darken towards purple as they age so that from a distance they could be mistaken for the flowers of Belladonna—not surprising since the potato is also a nightshade. Just the same, the flowers put on a pretty good show and they attract certain types of small black wasps and even an occasional butterfly, so I suspect there may be a subtle scent that is not easily detected by humans.
All potatoes are technically perennial; the tops die back after flowering and new plants emerge in the spring from the tubers produced the previous season. Where the ground freezes, potatoes must be dug for overwinter storage, and while the phureja species is somewhat tolerant of light mountain frosts, it cannot survive a hard, deep freeze. So once the tops have turned yellow and fallen over, you have a ready signal to dig the tubers. And what a joy that is! It’s like panning for gold—only in this case, the gold is good enough to eat.
By contrast, Papa Chaco claims more mundane origins: It is a Peruvian species of Solanum tuberosum, although an unusual one with a peculiar name. It has also been available to American growers for several years and has adapted itself quite well to our north-of-the-equator climate conditions. The potato was accessioned by the USDA from Peru in 1998 (its GRIN number is PI 611078) and has been traded among members of Seed Savers Exchange since then.
Like Yema de Huevo, this potato is extremely productive, and it will overwinter in the ground without protection, provided the frost line is not too deep. It is also a study in contrasts, for while the egg yolk potato is small and round, this potato is very large and showy. Many American potato growers consider it a fingerling due to its elongated shape, but the tubers are not as diminutive as the term fingerling would imply. In fact, the Peruvian name chaco does not refer to the shape, but rather to an ancient use of the potato in indigenous cookery. Because the potato has reddish or pink flesh, it can sometimes acquire a bitter taste, depending on soil and growing conditions, but especially due to the stress of late blight or exposure to daylight (which turns the outer part of the tubers green).
This bitterness is the result of two glycoalkaloids: chaconine and solanine, whose similar molecular structures have been isolated only within the past 30 years. Ancient Peruvians created an antidote to this bitterness, which is a natural defense mechanism in potatoes against predators and nematodes, by eating the potatoes with a sauce based on a special kind of clay. Chaco is edible organic clay derived from fossilized sea plants and animals. It is found in the Andes and was mined by the ancient peoples there for its numerous medicinal properties. The clay actually negates the toxins by blocking the body’s ability to absorb them and thus enabled ancient peoples to consume otherwise inedible potatoes during times of severe food shortages.
The good news about Papa Chaco is that over the years the high level of toxins have been bred out through careful selection, thus the modern version of this potato, the one now grown in the United States, is genetically different from the ancient cultivar that was prone to bitterness. Keep in mind that all pink, red and violet potatoes share this trait, and that late blight or physical damage to the tubers will automatically increase the level of toxins. The toxins are very easy to detect due to their unpleasant bitterness, and cooking will not destroy them. Lest you imagine that Papa Chaco with clay sauce sounds like the ultimate in bad hospital fare, this dish combination has assumed such an iconic role in the tourist cuisine of Peru and Bolivia that you are likely to find it served in even the most prestigious restaurants and hotels. The traditional way to prepare the potato was to grill or roast it (see my recipe at right). It makes a very showy meal indeed!
Papa Chaco sports the most extraordinary lavender-rose skin with marbled rose-purple flesh; these colors are especially intense when the potatoes are freshly dug. The tubers are long and somewhat pointed on both ends, but they can also curve into a half-moon shape when the tubers are long — up to 8 inches in some cases.
Furthermore, there is no mistaking the plants for common potatoes. The new leaves are tinged with deep black-green and remain that color as they mature. The stems of the plants are tall, spindly, and brown. They seem almost stick-like in their erect habit of growth and can attain a height of as much as 36 inches. Like Yema de Huevo, the flowers are colored, but in this case they are pale lilac with a white stripe or “star” in the center.
The plants also produce numerous seed balls with viable seeds, so it is possible to do a little plant breeding with this potato even at low altitudes (some Andean potatoes require a high altitude for good seed set). Thus from a potato aficionado’s standpoint, this one is lots of fun to grow, but it does require plenty of room, unlike Yema de Huevo, which can be grown in tubs.
As a general rule, Papa Chaco should be planted about 14 inches apart in order to give the plants enough space to tuberize — each plant will yield a surprising number of potatoes, sometimes 15 or 20, depending on the fertility of the soil. Several Peruvians have told me that one reason the potato plant is so tall and spindly is that it was developed by selection to be inter-planted with oca or one of the other Andean plants such as maca which grows close to the ground. This would make sense given the necessary crowding that occurred in the terraced fields used by the ancient Incas. It certainly suggests that American gardeners can find alternative crops to interplant between the rows of Papa Chaco: lettuce for example, or small radishes, mustard, even spinach. This plan works especially well if Papa Chaco is planted late (it is considered a late variety) because it seems to tuberize better in September-October with declining day length.
No matter, whichever variety you choose, whether Yema de Huevo or Papa Chaco, there will be no mistaking the accolades when they are brought to the table. Their flavors are so amazing and intense, their colors so eye-stopping, that you will be glad you added them to your culinary experience.
Papa Chaco Potato with Pumpkin Sauce
One of the best traditional ways to prepare these potatoes is to roast them whole in the skins in an oven or to grill them over hot coals. This very simple Peruvian preparation method, called Pepián de Papa Chaco, is a perfect match for the salsa that goes with them since it is intended as a dip.
Serves 4 to 6
• 3 pounds of Papa Chaco (or potato of your choice)
• 1 pound Yema de Huevo potato (optional)
• 1/2 cup olive oil or peanut oil
• 1 tablespoon finely minced garlic
• Sea salt to taste
• Salsa de Pipián (see below)
1. Wash and trim the potatoes, then dry them thoroughly.
2. Combine the oil and garlic and set aside.
3. Preheat the oven to 375 degrees Fahrenheit.
4. Brush the potatoes lightly with the oil and garlic and roast them on a baking sheet for 15 to 20 minutes or until tender.
If grilling over hot coals, baste the potatoes while they cook, turning them from time to time so that they do not scorch. Scatter coarse sea salt over the potatoes and serve them immediately on a warm platter, giving each person a fork and a small bowl of Salsa de Pipián for dipping.
Salsa de Pipián
• 3 Cups cooked, pureed pumpkin
• 1/2 Cup coarsely ground unsalted peanut butter
• 1/2 Cup chopped cilantro (leaves only)
• 1/3 Cup olive oil or peanut oil
• 3 Tablespoons garbanzo flour
• Grated zest of 1 lime
• Juice of 1/2 a lime or to taste
• Hot pepper to taste (such as Aji Limó, Aji Mirasol, or other hot yellow pepper)
• Finely chopped peanuts (optional)
1. Combine the pumpkin puree, peanut butter, and cilantro in a blender or food processor. Work until the mixture is light and fluffy.
2. Heat the oil in a deep stewing pan and when it becomes crackling hot, add the garbanzo flour. Stir vigorously until the flour begins to change color and smell toasty.
3. Reduce the heat and add the pumpkin puree and stir until thoroughly combined.
4. Add the lime zest, lime juice, and hot pepper to taste (the salsa should be spicy).
5. Adjust seasonings with salt, and once the salsa is hot, serve immediately as a dip in individual bowls.
Finely chopped peanuts can be served over the salsa as garnish.
William Woys Weaver is an internationally known food historian, author, and heirloom gardener living in Devon, Pennsylvania.