Best baked mac 'n' cheese

Ingredients:

• 450 g of pasta horns
• Half a loaf of yesterday's French bread
• 110 g unsalted butter
• 1/4 cup premium flour
• 2 tsp mustard powder
• 1/4 tsp cayenne pepper
• 3 cups of milk
• 220 g fontina cheese, grated (about 2 cups)
• 220 g Gruyere, grated (about 2 cups)
• 450 g sharp yellow cheddar, grated (about 4 cups)

Preparation:

1. Preheat oven to 175°C.
2. Bring a large saucepan of salted water to a boil over high heat. Add the pasta and cook until slightly tender, about 6 minutes. Set aside 1 cup of the water, drain the rest, and rinse the pasta under cold water.
3. Meanwhile, remove the crusts from the bread and cut it into 2.5cm-thick cubes. Pulse in a food processor until the bread is broken into bean-sized pieces.
4. In a large skillet over medium heat, melt 3 tablespoons of butter. Add the breadcrumbs and cook, stirring, for 5-10 minutes. Remove from heat and season with salt and pepper to taste.
5. In a large saucepan over medium heat, melt 4 tablespoons of butter. Stir in the flour, mustard powder, and cayenne pepper. Cook, whisking constantly, until the mixture is golden brown, about 2 minutes. Stir in the milk and cook, stirring occasionally, until the sauce comes to a boil and thickens, about 7 minutes, then remove from heat. Stir in the fontina, Gruyere, and most of the cheddar, setting aside 1 1/2 cups, until the cheese is completely melted. Stir in the pasta, adding some of the cooking water if necessary to thin the sauce. Season with salt and pepper to taste.
6. In a small bowl, melt the remaining 1 tablespoon butter in the microwave. Grease a 9x13-inch glass or ceramic baking dish with the melted butter. Spread the mac and cheese in the prepared dish. Sprinkle the remaining cheddar evenly over the top, then top with the toasted breadcrumbs. Bake until the mac and cheese is heated through and bubbly, about 25 minutes. Let rest for 10 minutes and serve.