Get ready to love this oven-baked Brussels sprout casserole! It's a cozy mix of fresh sprouts, creamy sauce, crunchy walnuts, and crispy breadcrumbs. This mouthwatering recipe is the ideal savory side dish that's perfect for gatherings.
Preheat the oven to 425° F. Spray a 13 x 9-inch baking dish with cooking spray. Toss the Brussels sprouts with the oil, salt, and pepper and arrange in the prepared dish.
Cook for 30 minutes, tossing halfway through.
While the Brussels sprouts are cooking, melt the butter in medium saucepan over medium heat. Add the bread crumbs and walnuts and cook for 3 to 4 minutes, until fragrant and lightly browned. Remove to a bowl.
In a saucepan, add the remaining 2 tablespoons of butter. Add the garlic, and cook for 30 seconds. Add the flour and cook for 3 to 4 minutes. Gradually add the half and half, whisking well to combine. Bring to a simmer, and cook for about 5 minutes, until the sauce starts to thicken.
Turn the heat to low, and add 2 ounces of the Gruyere and the parmesan. Stir until the cheese melts. Stir in the cayenne pepper, and season to taste with salt and pepper. Pour the sauce over the roasted Brussels sprouts. Sprinkle with the remaining Gruyere cheese and then top with the breadcrumb mixture.
Bake for 15 minutes longer, until golden brown. Allow to cool slightly before serving