I love roasted brussels sprouts and the pairing of the sprouts with potatoes in this creamy gratin is ingenious. This dish is served at a delightful little wine bar, Enoteca Vin, in Raleigh, North Carolina.
Melt butter and oil in a large deep skillet. Add brussels sprouts and minced shallot and saute until soft, about 8 minutes. Add white wine and continue to cook for 1 minute until evaporated. Season with salt and pepper. Add cream and bring to a simmer. Cool to room temperature.
Smear a 1 1/2-quart shallow casserole dish with butter. Reserve 2 tablespoons of Parmesan for the topping. Arrange the potato slices evenly over the bottom of the dish and season with salt and pepper. Using a slotted spoon, spread a layer of brussels sprouts over the sliced potatoes and sprinkle with Parmesan cheese. Continue layering until all of the potatoes and brussels sprouts and all but the reserved 2 tablespoons of Parmesan have been used. The last layer should be potatoes. Pour the cream over the potatoes and top with the remaining Parmesan. Cover with buttered foil and bake for 45 minutes.
Uncover the gratin and bake for 30 minutes longer, or until the potatoes are tender and the top is golden brown. Let sit for 15 minutes before serving.