Gruyere Mac and Cheese with Caramelized Onions

Directions

• Preheat oven to 375° F. Grease an 8×8 baking dish.
• In a large skillet, melt 2 tablespoons of the butter over medium heat. Add the onion and a pinch of salt and cook, stirring occasionally, until browned and caramelized, about 40 minutes.
• Cook the pasta according to the package directions, reducing the cooking time by 1 minute. Drain and set aside.
• In a large pot, melt the remaining 4 tablespoons butter over medium-high heat. Add the flour, whisking until combined, then cook for 1 minute. Add half the milk, whisking continuously until thickened, about 5 minutes, and then repeat with the other half of the milk. Add the Gruyere and Swiss and all but 2 tablespoons of the Parmesan and stir until the cheeses melt. Stir in the paprika, cayenne, nutmeg, mustard, and black pepper and salt to taste. Stir in the pasta and onions.
• Transfer the mixture to the baking dish and top with the panko, a pinch of salt, a few turns of pepper, and the reserved Parmesan and bake until the top is browned, about 25 minutes. Cool for 5 minutes and serve with an 8-ounce glass of milk.