From America's Test Kitchen Season 3: Pasta Classics
Unlike meat sauces in which tomatoes dominate, Bolognese sauce is about the meat, with the tomatoes in a supporting role. We wanted a traditional recipe for this complexly flavored sauce, with rich meatiness up front and a good balance of sweet, salty, and acidic flavors. We started simple—with just onions, carrots, and celery, sautéed in butter. A combination of meats, in the form of meat loaf mix, provided the right amount of meatiness. For the most tender texture, we cooked the meat just until it lost its pink color and didn’t let it brown. For dairy, which is used to tenderize the meat and give the sauce a sweet, appealing flavor, we used milk. Once the milk had reduced, we added white wine, which gave the sauce a delicate brightness. For the tomato element, diced canned tomatoes imparted sweet, acidic notes. Finally, we simmered the sauce at the lowest possible heat for about three hours and served it with rich, eggy fettuccine.
Don’t drain the pasta of its cooking water too meticulously when using this sauce; a little water left clinging to the noodles will help distribute the very thick sauce evenly over the noodles, as will adding two tablespoons of butter along with the sauce. If doubling this recipe, increase the simmering times for the milk and the wine to 30 minutes each, and increase the simmering time once the tomatoes are added to 4 hours