Step-by-step instructions for mixing and rolling the dough for Lasagna Bolognese noodles Get the Recipe: Lasagana Bolognese Watch the Video 1. Heat butter in a medium sauce-pan over medium heat until foaming. Add flour and cook, whisking constantly, 1 minute 2. Whisk in warm milk, 1/2-cupful at a time. Bring sauce to a boil, reduce heat, and simmer, whisking often, until the consistency of cream, 8–10 minutes 3. Add nutmeg and season with salt. Remove from heat, transfer to a medium bowl, and press plastic wrap directly onto surface; let cool slightly. Chill if not using right away.