You may already be aware that there are two kinds of sweet potatoes in U.S. grocery stores—the white kind no one buys, which look like regular potatoes, and the orange-fleshed ones everyone buys, labeled “yams,” but did you know that the orange-fleshed ones aren’t even really yams? THE GROCERY STORE IS LYING TO YOU! (Earth-shattering revelation!) Yams aren’t even potatoes. This issue came into stark relief the other week, when I asked B. to get some sweet potatoes and he came back with the white kind—in other words, the kind properly labeled “sweet potatoes,” even though I was looking for the orange kind but had refused to call them yams. I realized I had never even seen anyone purchase, let alone purchased and used myself, the white sweet potatoes. What were they for? What did they taste like?
I already used a few of that stash in a root vegetable and rice gratin, which was clearly the wrong application, because they just tasted like regular potatoes—a little softer than orange sweet potatoes but nowhere near as sweet, and piteously upstaged by candy-by-comparison parsnip and rutabaga. Then I realized I had seen a white-sweet-potato soup a while ago in Andrea Reusing’s “Cooking in the Moment,” which seemed to answer the exact question of the darn thing’s flavor profile. Loaded with apples, miso, sake, ginger, cream, and white wine, the recipe was clearly fine-tuned to complement the subtle flavors lurked within the potato, and it did. It’s an extremely sophisticated soup (I can say this because it’s not my recipe), and if you’ve ever had white sweet potatoes or wondered what on earth they were for, this dish will more than answer your question. It makes about 6 servings.
• 2 lbs. white sweet potatoes (the cashier thought they were Yukon Golds—I told you no one buys these—so she rang them up at 59 cents a pound. I did not correct her, but one was rotted and I had to throw it out, so karmic balance was achieved), peeled and cut into 1/2-inch rounds: $1.20 (they’re normally about $1.29/lb. or so)
• 3 onions, sliced pole to pole (if you don’t want them becoming stringy and wrapping around your utensil): 60 cents
• 3 Granny Smith apples: 75 cents
• 4 garlic cloves, chopped: 4 cents
• 2 T chopped ginger: 10 cents
• 3 T white miso: 20 cents
• 1/4 cup dry white wine: 44 cents
• 1/2 cup sake (I cheated and used Chinese cooking wine, which is $1.78 for a huge bottle and also fermented from rice): 60 cents
• 2 T mirin: 30 cents
• 1/2 cup heavy cream: 30 cents
• Salt & pepper: 2 cents
• 2 T canola oil: 6 cents
TOTAL: $4.61/6 = 77 cents/serving
Heat the canola oil in a large soup pot with lid over medium heat. Add the onions, garlic, ginger, and a large pinch of salt and pepper. Reduce heat to medium-low, cover, and cook until onions are softened but not browned, about 20 minutes.
Meanwhile, peel and slice the potatoes, if you haven’t already.
Add the white wine and cook, uncovered, until slightly reduced, about 5 minutes. Add the sweet potatoes, 5 cups water, and the sake, mirin and cream, along with another large pinch of salt. Bring to a boil, reduce to a simmer, cover, and cook for about 6 minutes, until sweet potatoes are partially tender.
Meanwhile, peel the apples, core them, and cut them into half-inch chunks.
Add the apple chunks to the soup and cook (still covered) for 10 minutes longer, or until the potatoes are completely tender.
Remove from the heat and stir in the miso.
Purée until smooth with an immersion blender, or in batches in a regular blender. Adjust seasoning, then serve. I had some green onions all ready to put on top as a garnish, but after I tasted it, I realized it didn’t need anything muddying it up, so I recommend serving it as-is, so the sweetness from the apples and miso and sharpness from the miso and sake come through.