• Preheat the oven to 350°F (180°C). Butter the casserole dish.
• Cook pasta: Bring a large pot of water to a boil. Add salt generously and cook the macaroni for 1 minute less than indicated on the package. Drain well.

  9 oz macaroni
• In the meantime, prepare the rest of the recipe.
• Grate both types of cheese. Set them aside.

  1¾ cups sharp cheddar + 1 ⅓ cup Gruyere cheese

Make the sauce:

• Roux: Melt the butter in a large saucepan. Sprinkle the flour on top and constantly stir for about 1 minute until the flour turns lightly golden.

  2 tablespoons butter + ⅓ cup all-purpose flour
• Add milk: Slowly add the milk while whisking continuously to avoid lumps. Whisk until the mixture is lump-free.

  1 ½ cups full-fat milk
• Add mustard, sweet paprika, salt, and pepper, and stir well to mix.

  1 ½ teaspoon Dijon mustard + ½ teaspoon sweet paprika powder + ½ teaspoon fine sea salt + ⅛ teaspoon black pepper
• Simmer the white sauce for a couple of minutes until thickened while stirring constantly.
• Add cheese: Turn off the heat and stir 2 cups of the Cheddar cheese and all the Gruyere cheese into the sauce. Stir well until almost completely melted. Crack the egg on top and stir it in as well. Adjust the taste with more salt if necessary.

  2 cups of the grated Cheddar + all Gruyere cheese + 1 egg
• Add macaroni and stir well to combine.

Bake mac and cheese:

• Assemble the dish: Pour the mixture into the prepared casserole dish. Sprinkle with the remaining ⅓ cup of Cheddar cheese.
• Bake: for 20-25 minutes until the top of the dish is lightly golden. Don’t overbake the dish, or it will become dry. Serve immediately.