Preheat the oven to 400°F. Grease a 9x13 inch baking dish.

Bring a large pot of salted water to a boil. Add the halved Brussels sprouts and cook for 5 minutes until slightly tender but still firm. Drain well and set aside.

In a large saucepan, melt the butter over medium heat. Add the minced garlic and cook for 1 minute until fragrant.

Sprinkle the flour over the buBer and garlic, whisking constantly for 1 minute to create a roux. 5. Slowly pour in the heavy cream, whisking continuously to prevent lumps from forming. Cook for 2-3 minutes until the sauce begins to thicken.

Stir in the nutmeg, salt, and pepper. Remove from heat.

Add 1 1/2 cups of the grated Gruyere cheese to the sauce, stirring until melted and smooth.

In a large bowl, combine the blanched Brussels sprouts with the cheese sauce, gently toss to coat evenly.

Transfer the Brussels sprouts mixture to the prepared baking dish.

Sprinkle the remaining 1/2 cup of Gruyere cheese and the Parmesan cheese over the top. 11. Bake in the preheated oven for 20-25 minutes, until the top is golden brown and bubbly.

Allow to cool for 5 minutes before serving.