Saute onion in butter over medium heat. Stir in flour, cook for 3 minutes constantly stirring. Add in salt, pepper and nutmeg.
Slowly pour in milk and 1 cup of half and half. Stir until thick.
Mix the rest of the half and half with 1 egg yolk. Stir into sauce. Bring to a simmer and remove from heat.
Brown Premio sausage with the garlic.
In a seperate bowl combine the ricotta, 1/2 the Parmesan cheese and the eggs.
Cook the noodles and drain.
Start to layer the lasagna in a 9 x 13 pan, beginning with white sauce, then the noodles, ricotta mixture, Premio sausage and mozzarella. Repeat layers and top with remaining sauce and mozzarella cheese. Sprinkle the top layer with paprika. Bake at 375 degrees for 20-30 minutes or until bubbly. Serve with homemade pesto and tomato sauce.