Step 1Heat the oil, 3 tablespoons butter and the onion in a large high-sided skillet over medium heat and cook, stirring often, until the onion is translucent, about 5 minutes. Add the celery and carrots and cook for about 2 minutes more, stirring to coat the vegetables with the butter.
Step 2Add the ground beef, a pinch of salt and a few grindings of pepper and cook, crumbling the meat with a fork, until it has lost its raw, red color. Add the milk and simmer it gently, stirring frequently, until it has bubbled away completely, about 15 minutes.
Step 3Add the nutmeg and stir. Add the wine and let it simmer until it has evaporated, about 25 minutes. Add the tomatoes and stir thoroughly to coat all the ingredients well. When the tomatoes begin to bubble, turn the heat down to cook the sauce at the laziest of simmers, uncovered, for 3 hours or more, stirring from time to time. You will need to add water to the pan occasionally to prevent the meat from sticking.
Step 4Taste for salt and toss with cooked, drained pasta and the remaining tablespoon of butter. Serve with freshly grated Parmesan on the table.