For meat sauce, in a 4-quart Dutch oven cook sausage, ground beef, onion, carrot, sweet pepper, celery, pancetta, and garlic over medium-high heat until meat is brown, using a wooden spoon to break up meat as it cooks. Drain off fat.
Stir in tomatoes, tomato paste, wine, dried basil and oregano (if using), salt, and black pepper. Bring to boiling; reduce heat. Simmer, covered, for 30 minutes, stirring occasionally. Stir in milk and fresh basil and oregano (if using).
Meanwhile, cook lasagna noodles according to package directions; drain. Rinse with cold water; drain again.
To assemble lasagna, spread about 1 cup of the meat sauce in the bottom of an ungreased 3-quart rectangular baking dish. Top with three of the noodles and 2 cups of the meat sauce. Top with three more noodles and half of the Porcini-Parmesan Sauce. Repeat layering noodles, meat sauce, and Porcini-Parmesan Sauce. Top with the remaining three noodles and the remaining meat sauce. (To serve today, omit Step 4. Continue as directed in Step 6, except bake, covered, for 30 minutes.)
Cover baking dish with plastic wrap, then with foil. Chill for 2 to 24 hours. To serve, let stand at room temperature for 30 minutes. (Or freeze for up to 1 month. To serve, thaw in the refrigerator overnight [lasagna may still be a bit icy].)
Preheat oven to 350 degrees F. Remove plastic wrap; re-cover with foil. Place lasagna in a foil-lined shallow baking pan. For chilled lasagna, bake for 30 minutes. Sprinkle with 1 cup Parmesan cheese. Bake, uncovered, for 20 to 30 minutes more or until heated through. (For partially thawed lasagna, bake for 45 minutes. Sprinkle with 1 cup Parmesan cheese. Bake, uncovered, for 20 to 30 minutes more or until heated through.) Let stand for 20 minutes before serving. If desired, sprinkle with additional Parmesan cheese.
In a small bowl combine mushrooms and enough boiling water to cover. Let stand for 10 minutes; drain. Rinse with cold water; drain again. Chop mushrooms; set aside.
In a large saucepan cook and stir garlic in butter over medium heat for 30 seconds. Stir in flour until combined. Slowly stir in milk and wine or chicken broth (milk may curdle if using wine, but sauce will appear smooth when finished). Cook and stir until thickened and bubbly. Remove from heat. Stir in mushrooms, ricotta cheese, Parmesan cheese, parsley, basil, and salt. Makes about 4 1/2 cups.