To Make Ahead: You can prepare this spaghetti casserole up to one day in advance. Follow the recipe instructions through step 6 (just before baking), then let it cool completely. Cover tightly with plastic wrap and refrigerate until you’re ready to bake. Alternatively, you can prepare the sauce, noodles, and cheese layer separately 1 to 3 days ahead and assemble the casserole just before baking. To Freeze: Prepare the casserole completely up to the baking stage. Cover it securely with greased aluminum foil and freeze for up to three months. When you’re ready to enjoy, thaw it in the refrigerator for 1 to 2 days, then bake covered for about 20 minutes, followed by 20 to 25 minutes uncovered. If baking straight from frozen, bake covered for roughly 40 minutes, then remove the cover and bake an additional 30 to 40 minutes or until the casserole is hot and bubbly throughout. Vegetarian Million Dollar Spaghetti: For a meatless version, simply omit the meat or substitute it with your preferred plant-based meat alternative. Ground Beef vs. Sausage: This recipe uses both ground beef and Italian sausage for flavor, but you can use either one alone if you prefer. If you use both, save any leftover Italian sausage for another dish like Baked Ziti or Pizza Casserole. Pasta: While spaghetti is traditional for Million Dollar Spaghetti, feel free to use any pasta shape you like best.