Packed with antioxidants, this dish is as healthy as it is flavorful. It uses a lightened-up bechamel sauce, so you get the richness without the butter. And the fancy sage garnish couldn’t be easier: All you need is 10 seconds to flash-fry the fresh leaves in some vegetable oil.
Yield: Serves 6 to 8
- 2 tablespoons extra-virgin olive oil
- 3 tablespoons all-purpose flour
- 1 cup whole milk
- 1/4 cup plus 1 tablespoon freshly grated Parmesan
- 20 fresh sage leaves, plus 1 tablespoon chopped fresh sage
- Coarse salt and freshly ground pepper
- 2 pounds sweet potatoes, peeled and sliced 1/4 inch thick
- 1 head cauliflower, quartered and sliced 1/4-inch thick
- Vegetable oil, for crisping sage
1. Heat oven to 350° F. Heat olive oil in a small pot over medium heat. Add flour and cook, stirring, 1 minute. Slowly whisk in milk and 1 cup water. Cook, whisking, until thick enough to coat the back of a spoon, about 12 minutes. Remove from heat and stir in 1/4 cup Parmesan and the chopped sage. Season with salt and pepper.
2. Pour a third of the sauce in the bottom of a 9-by-13-inch casserole dish. Arrange a third of the sweet potato and cauliflower slices along the bottom. Season with salt and pepper. Repeat twice with remaining sauce and vegetables. Cover dish with parchment-lined foil and bake until vegetables are tender, about 1 hour. Raise oven temperature to 425° F. Remove foil and sprinkle with remaining tablespoon of cheese. Bake until golden brown, about 20 minutes. Let stand 10 minutes before serving.
3. Meanwhile, crisp sage leaves: Heat 1 inch vegetable oil in a small pot over medium-high heat until surface is shimmering slightly. Add a few leaves at a time (they’ll bubble up) and cook until crisp, but still bright green, about 10 seconds. Transfer to a paper towel to drain. Season with salt. Top gratin with leaves.