Makes 4 cups
Bring a teakettle of water to a boil. Put the dried mushrooms in a small bowl, cover with 1 cup boiling water, and let them soak for 20 minutes. Drain the mushrooms, reserving the soaking liquid, and chop them finely. Strain the soaking liquid and set it aside.
Heat the oil in a large saucepan over medium heat. Add the chopped mushrooms, pancetta, onion, carrot, and celery and cook until the pancetta and vegetables begin to brown, stirring occasionally, about 12 minutes. Add the ground beef, pepper flakes, garlic, salt, and pepper and cook, breaking up the ground beef with a wooden spoon, until it changes color, about 5 minutes. Stir in the tomato paste and cook, stirring occasionally, until the meat begins to brown in the bottom of the pan, about 12 minutes.
Reduce the heat to low, pour in the wine, milk, stock, and the reserved mushroom soaking liquid. Use the spoon to scrape the bottom of the pan clean. Simmer the sauce partially covered until it is very thick, 1 1/2 to 1 3/4 hours.
Note: When tossing this sauce with pasta, reserve 1/4 cup of the pasta cooking water to splash in if it seems too dry or "tight."
Source: Curry, Lynne. "Bolognese Meat Sauce." Pure Beef: An Essential Guide to Artisan Meat with Recipes for Every Cut. Pennsylvania: Running Press Book Publishers, 2012. 90-91. Print.