Many traditional bolognese sauces are simmered for hours, but this one just needs a short time on the stove. It is easy to make ahead and reheat if you are doing this intentionally, cook it up through the second step, and refrigerate it in a sealed container or covered pot for up to three days. Reheat the sauce over low heat and stir in the milk and cheese just before serving. I have also made this with ground turkey, for a lighter version, and its delicious. Ground nutmeg is a seasoning that you might think of adding as well; its very traditional. Sometimes just a bit of sauted pancetta is also incorporated into the sauce, which you are welcome to add with the onions and other vegetables. This is a thick sauce meant to really highlight the meat as the primary ingredient. You could make a thinner sauce by adding another can of tomato puree (and then you'll have enough sauce for 1 1/2 pounds of dried pasta).