To make the meat sauce, heat the olive oil in a sauté pan over a medium heat. Add the onion, celery and garlic and sauté for a couple of minutes until just beginning to brown. Add the minced beef and continue to fry over a high heat for 3-4 minutes, breaking up any lumps with a wooden spoon as it browns.
Stir in the cloves and then add the cinnamon stick, oregano, bay leaves, tomatoes, tomato purée, wine and 100 ml of water. Season to taste and mash down the plum tomatoes to break them up, then simmer for 30-40 minutes, stirring occasionally until the sauce has nicely reduced and thickened. Remove and discard the cinnamon and bay leaves.
Bring a large pan of salted water to the boil and cook the pasta according to packet instructions for about 12 minutes or until al dente. Drain into a colander and leave to cool slightly.
Meanwhile, make the white sauce. Melt the butter in a small pan and then stir in the flour and cook for another minute over a medium heat. Gradually whisk in the milk, then bring to the boil, stirring. Reduce the heat to low and simmer for about 5 minutes, stirring occasionally. Season to taste and add the nutmeg. Keep warm over a low heat.
Preheat the oven to 180°C/350°F/Gas Mark 4. Stir 250 ml of the white sauce into the warm pasta with the beaten eggs and half of the cheese. Grease a 23 x 33 cm ovenproof dish that is about 7cm deep with butter and put one third of the pasta mixture in the base of the dish, then spread over half of the meat sauce. Add another third of the pasta and then add the rest of the meat sauce, then cover with a final layer of the pasta. Spoon the remaining white sauce on top. Mix the rest of the cheese with the breadcrumbs and sprinkle on top. Bake for 40 minutes until bubbling hot and golden brown.
Leave the pastitsio to settle for about 5 minutes after coming out of the oven and then serve with the Greek salad and crusty bread.