½ pound unsalted butter
1 white onion, thinly sliced
1 leek, white part only, sliced and washed
1 small head of fennel, sliced thin
Salt and white pepper, to taste
1 cup water
3 pounds washed baby spinach (or 3 bunches of green Swiss chard, stemmed, chopped, and washed thoroughly)
2 tablespoons olive oil
1. For the soubise onion puree: Melt butter in a heavy-bottomed sauce pot on low heat. Add the onion, leek, and fennel. Season well with salt and white pepper. Cook slowly on no more than medium heat until the vegetables start to get tender and translucent, about 15-20 minutes. But make sure they do not brown. Add the water, cover tightly, and simmer for 20 minutes, stirring occasionally.
2. When vegetables are very tender, puree until smooth in a blender. The mixture should resemble a frothy, creamy soup. This can be done up to one day in advance.
3. To finish, just before service: Gently warm the soubise, and set aside. Heat olive oil over high heat in a large Dutch oven, and sweat the spinach (or chard stems first, then leaves) until tender. Fold in the onion puree and heat through. Serve immediately.
Per serving: 231 calories, 5 grams protein, 8 grams carbohydrates, 1 gram sugar, 22 grams fat, 49 milligrams cholesterol, 246 milligrams sodium, 4 grams dietary fiber.