Step 1

Melt butter in a small saucepan over medium-low heat; whisk flour into the melted butter until dissolved, 5 to 10 minutes. Season with salt and white pepper. Pour milk into the flour mixture; cook and stir until sauce is smooth and thickened, 10 to 15 minutes.

Step 2

Bring a large pot of lightly salted water to a boil. Cook pasta in the boiling water, stirring occasionally until cooked through but firm to the bite, 12 minutes. Drain and transfer to a serving bowl.

Step 3

Remove sauce from heat and stir in egg yolks and nutmeg until well incorporated. Pour sauce over pasta; toss to coat.

Step 4

Cook and stir sausage in a skillet over medium heat until browned and cooked through, 5 to 10 minutes. Stir sausage into pasta; season with salt and white pepper.