Bring a large pot of lightly salted water to a boil. Add penne and cook for 8 to 10 minutes or until al dente; drain and return to pan.
Melt butter until golden brown and pour over penne, add half of the Parmesan cheese, nutmeg, salt, pepper and toss well; allow to cool. Add eggs and toss again; set aside.
To make meat sauce: Gently fry onion and garlic in butter in a frypan until onion is soft. Increase heat and add beef mince; stir well. Cook until meat begins to brown. Add tomato paste, wine, stock, parsley, salt and pepper. Cover and simmer over low heat for 20 minutes.
To make cream sauce: Melt butter in saucepan, stir in flour and cook gently for 2 minutes. Pour in milk all at once and bring to a boil, stirring constantly. Boil gently for 1 minute. Add nutmeg, salt, pepper and cool slightly before stirring in beaten egg. Transfer 1/2 cup of this sauce to the meat sauce.
To assemble: Grease a 20x30cm baking dish. Spoon half of the prepared penne evenly in the bottom and top with meat sauce. Top that with remaining penne. Pour on cream sauce and spread to completely cover. Sprinkle remaining cheese on top.
Bake in a preheated oven for 50 minutes or until golden brown. Let stand 10 minutes before cutting into squares to serve.