Bring a large pot of salted water to a boil. Add pasta and cook according to package instructions until al dente. Reserve 1/2 cup of pasta water and drain the pasta.

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

Sprinkle in the flour and whisk constantly for 1–2 minutes until the mixture is bubbling but not browned to form a roux.

Gradually add the milk, whisking continuously to prevent lumps. Cook for 4–5 minutes until slightly thickened.

Stir in salt, pepper, and ground nutmeg. Add grated cheddar and mozzarella cheeses, stirring until melted and the sauce is smooth. Remove the pan from heat and stir in the parmesan cheese.

Add drained pasta to the sauce, stirring to coat evenly. If the sauce is too thick, stir in a little reserved pasta water until desired creaminess is achieved.

Taste and adjust seasoning if needed. Serve immediately, garnished with chopped parsley if desired.