1. Melt the butter and the oil in a large saucepan over medium heat. Add the pancetta and cook 2 minutes, until it gives off some fat. Add the onion, celery, carrot, and garlic and cook, stirring, 10 minutes, or until softened but not browned.

2. Stir in the ground round and cook 10 minutes, stirring and breaking it up with a spoon, until browned. Stir in the tomatoes and their juices, stock, and tomato paste, and season. Bring to a boil.

3. Reduce the heat and partially cover the saucepan. Simmer, stirring occasionally and adding more stock, if needed, for 1½ hours. Stir in the milk and simmer for 30 minutes more, until thick and well flavored.

4. Bring a saucepan of lightly salted water to a boil, add the pappardelle, and cook until al dente. Drain well. Transfer to a serving bowl and add the ragù. Toss and serve hot, with the Parmesan.

Variation:

Pappardelle alla Bolognese: For a richer sauce, substitute 7 oz (200g) ground round, 7oz (200g) ground pork, and 4 oz (115g) chopped chicken livers for the ground round. Add ¼ cup red wine to the browned meats and boil until most of the wine has evaporated. Replace the milk with 1/3 cup heavy cream.