This is one of my favorite recipes, not only because it's so good, but it only serves 2-3 people, depending on your appetite. My hubby doesn't eat leftovers so I get to eat whatever is left the next day.
Cook pasta; drain and return to pan. Stir in 4-1/2 tsp melted butter, 8 tsp parmesan cheese, 1/2 beaten egg. Reserve other half of beaten egg for later. Set aside.
Cook ground beef and chopped onion in skillet until meat loses its pinkness and the onion softens. Drain excess fat from pan.
Stir in tomato sauce, salt, mint flakes if using, cinnamon, nutmeg, and pepper. Set aside. (The recipe calls for 1/2 can of tomato sauce but I always use a whole can.)
Melt 2 T butter in a saucepan. Then mix in flour and 1/4 tsp salt. Slowly stir in milk, stirring well after each addition so no lumps form. Cook and stir on medium high until cream sauce starts to thicken. Stir for one more minute; then remove from heat.
Pour other half of beaten egg into cream sauce, stirring briskly. Blend in remaining parmesan cheese.
Layer half the pasta in a 2 quart baking dish. Spoon meat mixture over the top, then the remaining pasta. Pour cream sauce over the top to completely cover the pasta.
Bake, uncovered, at 350 degrees for about 40 minutes, or until hot and lightly browned. Let stand 10 minutes before serving.