Cook your pasta until just almost al dente in salted water. Reserve 2 cups of pasta water for the meat sauce. Toss the pasta with parmesan, nutmeg, and eggs.
In a large pot, heat olive oil. Add diced onion and sauté until translucent. Add ground beef and cook until no longer pink. Mix in tomato paste, diced tomatoes, spices, and sugar. Add reserved pasta water, simmer for 30 minutes.
Prepare béchamel: melt butter, whisk in flour, gradually add warmed milk, season with salt. Cook, whisking constantly until thickened. Beat in eggs and cook for an additional 2 minutes.
Preheat oven to 420°F. Spread half of pasta in a baking dish, top with meat sauce, then remaining pasta. Pour béchamel over the top and sprinkle with parmesan cheese.
Bake for 45-50 minutes until golden. Let stand 20 minutes before slicing.
Notes
This traditional Greek pastitsio is perfect for family dinners and special occasions.