Using a stand mixer if available beat eggs, parmesan cheese and butter together.
Cook spaghetti according to the directions on the package. Pour drained pasta right into bowl with egg and butter mixture. Use mixer to help mix and break up pieces of spaghetti.
Lightly grease a 9 x 13 inch baking dish. Pour half of spaghetti into dish.
Layer with half of ricotta cheese, half of sausage, half of spaghetti sauce and half of the mozzarella cheese. Repeat layers and cover with foil. Bake at 350°F for 30 minutes. Uncover and bake an additional 15 minutes or longer until cheese is melted.
Using a mixer will help break up the spaghetti into smaller pieces and be a very efficient way to cut the pasta with all the yummy flavors.
Italian sausage should be ground and removed from a casing and fully cooked before adding to the casserole.
Uncooked casserole can be covered tightly before freezing and defrost when ready to bake for a super easy freezer meal.
I prefer shredded Parmesan cheese, but grated Parmesan cheese can be used in a pinch.