Prepare the pasta according to package instructions.
In a saucepan, melt the butter over medium heat.
Whisk in the flour and cook for 2-3 minutes, stirring constantly.
Gradually whisk in the warm milk and cook until thickened, about 5-7 minutes.
Remove from heat and stir in the cheese blend until melted and smooth.
Season with nutmeg, salt, and pepper.
Combine the cooked pasta and cheese sauce in a baking dish.
Top with cubed pancetta and chopped parsley (optional).
Bake at 375°F for 20-25 minutes, or until golden brown and bubbly.
