Saute garlic in oil in a large saucepan over medium heat until lightly browned; add sausage and cook 2 to 3 minutes.
Add shallots to pan and saute 1 minute; stir in tomato puree and basil. Bring to a boil; reduce heat and simmer 40 to 45 minutes. Add salt and pepper to taste.
During the 40-45 minutes, combine ricotta mixture, and make Balsamella Sauce.
Combine ricotta, parsley, eggs, sugar, and pepper to taste, stirring until smooth; set aside.
To make Balsamella Sauce:
Melt butter in a sucepan over medium heat; remove from heat and add flour, stirring well.
Add milk and cream to saucepan and beat with a wooden spoon until smooth.
Bring to a boil over medium heat, stirring constantly; boil, stirring constantly, until thickened. Reduce heat and simmer 2 to 3 minutes. Stir in salt, pepper, and nutmeg.
Preheat oven to 350 degrees F.
Spoon a small amount of Balsamella Sauce in the bottom of a greased 9x13x2 inch baking dish; top with lasagne noodles to cover. Layer 1/3 each of ricotta mixture, remaining Balsamella Sauce, and fontina cheese. Sprinkle with 1 tablespoon Parmesan cheese and top with 1/4 of tomato sauce. Cover with a layer of noodles. Repeat layers twice.
Top with remaining tomato sauce and Parmesan cheese.
Bake at 350 degrees F for 50 to 55 minutes. Let stand at room temperature 20 minutes before serving.
Note: This makes a VERY full casserole. You may want to place the dish on a foil-lined baking tray to catch any boiled-over sauce.