Ragù Bolognese (North Italian Meat Sauce)

In a large skillet, melt 2 tablespoons butter over medium heat. Add onion, carrot, celery, and pancetta; cook, stirring often, until lightly browned, about 10 minutes. Transfer to a heavy large saucepan.

In the same skillet, heat olive oil over medium heat. Cook and stir ground pork and beef in hot oil until crumbly and browned. Pour in wine, increase heat to medium-high, and boil briskly, stirring constantly, until almost all of the liquid has evaporated. Transfer ground meat mixture to the saucepan with pancetta and vegetables. Set the skillet aside.

Stir beef stock and tomato paste into the saucepan; bring to a boil. Reduce heat and simmer, partially covered, for 45 minutes, stirring occasionally.