How to Make It
Put the oil, butter, and chopped onion in the pot, and turn the heat on to medium. Cook and stir the onion until it has become translucent, then add the chopped celery and carrot. Cook for about 2 minutes, stirring the vegetables to coat them well.
Add the ground beef, a large pinch of salt, and a few grindings of pepper. Crumble the meat with a fork, stir well, and cook until the beef has lost its raw, red color.
Add the milk and let it simmer gently, stirring frequently, until it has bubbled away completely. Add a tiny grating—about 1/8 teaspoon—of nutmeg, and stir.
Add the wine, let it simmer until it has evaporated, then add the tomatoes and stir thoroughly to coat all ingredients 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 to the surface. Cook, uncovered for 3 hours or more, stirring from time to time. While the sauce is cooking, you are likely to find that it begins to dry out and the fat separates from the meat. To keep it from sticking, continue the cooking, adding 1/2 cup of water whenever necessary. At the end, however, no water at all must be left and the fat must separate from the sauce. Taste and correct for salt.
Toss with cooked drained pasta, adding the tablespoon of butter, and serve with freshly grated Parmesan on the side.
Recommended pasta: There is no more perfect union in all gastronomy than the marriage of Bolognese ragù with homemade Bolognese tagliatelle. Ragù is delicious with tortellini, and irreproachable with such boxed, dried pasta as rigatoni, conchiglie, or fusilli. Curiously, considering the popularity of the dish in the United Kingdom and countries of the Commonwealth, meat sauce in Bologna is never served over spaghetti.