Heat the olive oil in a saute pan or large skillet over medium-low and, a minute later, add the onion, carrot, celery, and bacon or pancetta. Cook, stirring occasionally, until the vegetables are tender, 8-10 minutes.

Add the ground meat and cook, stirring and breaking up any clumps, until all browned, about 5 minutes. Add the wine or tomato juice, raise the heat to medium, and cook, stirring occasionally, until most of the liquid is evaporated, about 5-10 minutes.

Crush the tomatoes with a fork or your hands and add them to the pot; stir, then add the stock and the sprig of thyme. Turn the heat to low and cook at a slow simmer, stirring occasionally and breaking up the tomatoes and any clumps of meat that remain. After an hour or so, add salt and pepper. Cook for at least another hour, until much of the liquid has evaporated and the sauce is very thick.* (This sauce may be covered and refrigerated for a day or two, or put in a closed container and frozen for several weeks. Reheat before completing.)

Remove the thyme stem (leaves should have fallen off). Add the cream, half-and-half or milk and cook for another 15 to 30 minutes, stirring occasionally; taste and add more salt and/or pepper as needed. Serve over a thick, flavorful pasta.