In a large, heavy pot, heat the olive oil and butter. Stir in the onions and cook until translucent. Add the chopped carrots and celery. Cook for about 2 – 5 minutes, stirring well.
Add the ground meat, season with sea salt and fresh pepper. Crumble with a fork, stir well, and cook until the meat has lost its pink color.
Add the milk and let the mixture simmer gently. Stir frequently until the milk has evaporated. Add the freshly grated nutmeg. Add the wine, let simmer until evaporated.
Then add the tomato puree. Stir to mix well.
When the tomatoes begin to bubble, turn the heat down so that the sauce cooks at the laziest of simmers, with just an intermittent bubble breaking through the surface. Cook, uncovered, for 3 hours or more.