For the sauce:
1. Prepare the tomato sauce. In a saucepan melt the butter at medium heat. Add the pork and cook 3 minutes. Add the onion, carrot and celery; cook until tender, 5 minutes. Add the garlic and cook 1 minute. Add the wine and stir with a wooden spoon; lower the heat and cook until the mixture is reduced to half, 15 minutes. Add the cream and nutmeg; simmer for 5 minutes. Add the tomatoes, juice included, crushing them with a spoon. Cover the saucepan and simmer for 2 hours, stirring occasionally. Season with salt and pepper.
2. Prepare the white sauce. In a saucepan melt the butter at low heat. Add the flour and cook stirring for 1-2 minute. Remove from heat and add the milk stirring. Bring back to heat and cook for 20 minutes, stirring constantly. Season to taste.
3. Prepare the dish. In a large saucepan with plenty of boiling salted water cook the pasta. Drain under cold running water. Cover the bottom of an oven dish with a little tomato sauce, then a layer of pasta, more tomato sauce and white sauce sprinkled with cheese. Continue until ingredients are finished.
4. Preheat the oven to 400ยบ. Cover the dish with aluminum foil and cook for 20 minutes. Remove the foil and brown for some minutes.