Macaroni and Cheese Casserole with Caramelized Onions

Ingredients:

• 450 g of pasta horns
• 110 g (8 tbsp) unsalted butter
• 4 onions, thinly sliced
• 2 teaspoons fresh thyme leaves
• 1 tsp. granulated sugar
• 1 cup white wine
• 1 beef bouillon cube
• 1/4 cup flour
• 2 tsp mustard powder
• 1/4 tsp cayenne pepper
• 3 cups of milk
• 450 gr. sharp yellow cheddar, grated (about 4 cups)
• 450 g Gruyere, grated (about 4 cups)
• 1 container (170 g) deep-fried onions
• Chopped chives, for serving

Preparation:

1. Preheat oven to 175°C.
2. Bring a large saucepan of water to a boil over high heat and season with salt. Add the pasta and cook until slightly tender, about 6 minutes. Set aside 1 cup of the pasta cooking water, drain the rest in the sink, and rinse the pasta under cold water.
3. In a large skillet over medium heat, melt 3 tablespoons of butter. Add the onion, sprinkle with thyme, sugar, and 1/2 teaspoon of black pepper, and cook, stirring occasionally, until dark brown, about 20 minutes. Add the wine and bouillon cube and stir to dissolve. Cook until the liquid has reduced by half, about 5 minutes. Set aside.
4. In a large heavy-bottomed saucepan or Dutch oven, melt 4 tablespoons butter over medium heat. Stir in the flour, mustard powder, and cayenne pepper. Cook, stirring constantly, until smooth and lightly golden, about 2 minutes. Whisk in the milk. Cook, stirring occasionally, until the sauce comes to a simmer and thickens, about 7 minutes; remove from heat. Add the cheddar and 2 cups of Gruyere and stir until the cheeses are completely melted. Stir in the pasta, adding more of the reserved cooking water as needed to ensure a creamy sauce. Season with salt and pepper to taste.
5. In a small bowl, melt the remaining 1 tablespoon butter in the microwave. Grease a 9-inch (22.32 cm) metal baking dish with the melted butter. Spread half the pasta mixture into the prepared dish. Spread the onion mixture on top in an even layer, then add the remaining pasta. Sprinkle with the remaining Gruyere.
6. Bake until the pasta is heated through and the sauce is bubbling, about 20 minutes. Sprinkle with fried onions and return to the oven for 5 minutes. Let the casserole rest for 10 minutes, then sprinkle with green onions and serve.