Brussels Gratin

Position a rack in the lower third of an oven and preheat to 375°F (190°C). Butter a 9-by-13-inch (23-by-33-cm) baking dish.

In a large fry pan over medium heat, warm the oil. Add the shallots and cook, stirring occasionally, until the shallots are tender and almost translucent, about 3 minutes. Add the garlic and sauté until fragrant, about 1 minute. Add the brussels sprouts, sugar and 1 tsp. salt and cook, stirring occasionally, just until the brussels sprouts begin to soften, about 5 minutes. Transfer the vegetables to the baking dish and set aside.

In a large saucepan over medium-high heat, melt the butter. Add the flour and cook, stirring constantly, until the flour is thoroughly incorporated and lightly browned, about 2 minutes. Whisk in the milk, half-and-half, allspice, nutmeg, cayenne and a large pinch of salt and bring to a boil. Lower the heat to medium and simmer, whisking frequently, until just thickened, 4 to 5 minutes. Remove from the heat. Add a pinch of pepper and 1 cup (4 oz./125 g) of the Gruyère. Whisk until smooth, then add the remaining Gruyère 1 cup (4 oz./125 g) at a time, whisking after each addition until smooth. Add 3/4 cup (3 oz./90 g) of the Parmesan and whisk again until smooth. Taste and season with salt and pepper.

Pour the milk mixture over the brussels sprouts and toss to combine. Bake, uncovered, until the mixture is bubbling around the edges, 10 to 12 minutes.

Meanwhile, in a bowl, stir together the fried onions and the remaining 1/4 cup (1 oz./30 g) Parmesan.

Sprinkle the brussels sprouts evenly with the fried onions. Return to the oven and bake for 6 minutes more. Turn on the broiler and broil until the top is golden brown, about 2 minutes more.

Let cool for at least 10 minutes before serving. Serves 8 to 10.

Williams Sonoma Test Kitchen