I found this in an Italian cookbook by Marcella Hazan. Its a lovely rich sauce. Its the traditional recipe for Bolognese sauce which can be served with Tagliatelle, rigatoni, conchiglie or fusilli but is never served with Spagetti in Italy!
Put the oil, 3 tbsp butter and chopped onion in the pot, turn the heat to medium and cook, stirring the onion until it becomes translucent.
Add the celery and carrot and stir for two minutes while cooking to coat them well.
Add the ground beef, a large pinch of salt and a few grindings of black pepper.
Cook the beef while crumbling it with a fork until the beef has lost its red colour.
Add the milk and let it simmer gently, stirring frequently until the milk has completely bubbled away.
Add the nutmeg.
Add the wine and let it simmer until it has evaporated.
Add the tomatoes and stir well. When the tomatoes start to bubble turn the heat down so that it is just simmering with the occasional bubble breaking the surface.
Cook uncovered for 3 hours, stirring from time to time. While it is cooking you will find the sauce dries out so continue to add a 1/2 cup of water when necessary to stop it sticking. However there should not be water left at the end of the 3 hours. The fat will separate from the sauce and this should happen.
Taste and adjust seasoning if necessary and toss with the pasta and rest of butter. Serve with parmesan on the side.