To prepare Meat Sauce: combine the onion, garlic, and celery and saute over low heat in 2 tbsp butter until golden (8-10 min), stirring frequently. Remove to a heavy 3-4 qt saucepan. In same frying pan, saute the sausage and ground beef in the olive oil until lightly browned. Stir to break up lumps. Remove excess grease. Add the wine to the meat and boil, stirring constantly, until wine is almost evaporated. Add meat to saucepan with onion mixture and add the tomatoes, tomato paste, stock, and seasonings. Simmer, partially covered, for 1 hour, stirring occasionally.
To prepare Besciamella, melt 3 tbsp butter in a heavy 2-3 qt saucepan, over low heat. Stir in the flour and cook slowly 2-3 minutes, stirring constantly. Pour in the milk and cream slowly, stirring with a whisk to obtain a smooth sauce. Heat to boiling, stirring constantly, until sauce thickens. remove from heat and add 1 tsp salt and the nutmeg. Set aside. Makes 3 cups).
Butter a 9x13x3 baking dish. In a large 6-8 qt pot, cook the lasagna. When cooked, drain and cover lasagna with cold water, then lift out strips and drain on paper towels.
To assemble, spread a layer of meat sauce on bottom of baking dish to about 1/4" deep. Over this lay 1/3 of the noodles, then 1/3 of the Besciamella and 1/3 of the mozzarella. repeat 2 more times; layering the meat sauce, noodles, Besciamella, and ending with the mozzarella. Sprinkle top with grated parmesan and bake in a pregeated 350 oven until bubbly, about 30 minutes.