To prepare the Bolognese sauce, heat the olive oil in a large pot over high heat. Add the ground beef and cook, breaking up the chunks with a wooden spoon, until it is evenly browned, about 7 minutes. Using a slotted spoon, transfer the meat to a bowl and set aside. Return the pot to medium heat and add the pork. Cook, stirring frequently, until just cooked through, about 2 minutes. Add the carrot, onion, celery, and garlic and cook until the vegetables are tender, about 4 minutes. Return the ground beef to the pot. Add the wine, stock, tomato paste, tomatoes, thyme, rosemary, half of the parsley, and the salt and pepper. Bring to a boil. Lower the temperature to a slow simmer, cover, and cook for 40 minutes. For a creamier, thicker Bolognese sauce, whisk just enough of the milk into the flour to make a creamy paste. Whisk in the remaining milk, and then pour the mixture into the simmering Bolognese sauce; cook, stirring often, for 5 minutes. (I didn’t add the milk/flour mixture. I loved it sans the thickening agent.) The sauce can be stored, covered and refrigerated, for up to 4 days, or freeze in a quart container for up to 2 months. If cooking the pasta immediately, keep the sauce at a low simmer. Bring a large pot of water to a boil and season with salt. Cook the pasta in the boiling water until al dente, 2 to 3 minutes. Drain, and quickly return the pasta to the pot (it should have some cooking water on it.) Add the hot Bolognese sauce, the cheese and the remaining parsley, and stir or toss to combine. Serve immediately, piping hot.
