The recipe depends on what you mean by Bolognese Sauce. It's become something of a generic term for meat sauce, at least in the U.S., but classic "real" Bolognese Sauce is something a little more specific.
Marcella Hazan's recipe for Bolognese meat sauce in her wonderful cookbook, Essentials of Classic Italian Cooking, includes only 1/2 cup onion, 2/3 cup celery, and 2/3 cup carrots, which she cooks in a tablespoon of oil and 3 tablespoons of butter, before adding 3/4 pound of ground chuck and a little salt and black pepper. She then adds a cup of whole milk, saying to cook the meat in the milk before adding a cup of wine and then 1.5 cups of plum tomatoes to "protect it from the acidic bite of the latter." Most interesting, she uses no garlic, basil, or oregano, just "about 1/8 teaspoon" of freshly grated nutmeg. And she says to simmer it all for at least 3 hours.
I've never made anything from any of her cookbooks (and I think I have them all) that wasn't wonderful, very authentically Italian.