In a pan preferably just large enough to hold the ribs flat, heat a little neutral oil over medium heat. Add a half of a medium onion, chopped well, half of a large carrot, chopped well, and half a celery stalk, chopped well. Add a pinch of salt and sauté, stirring occasionally till the onion is soft and starting to brown in spots.
Increase the heat to med-high and cook, stirring here and there, till a bit more browning has occurred. If you wish, stir in a teaspoon or so of tomato paste (optional). If you have some available, deglaze the pot with wine (I prefer white here), about 1/4 cup, scraping the bottom of the pot, and cook, stirring constantly, till the wine has reduced to practically nothing. (If you don't have wine use water.
Add the bones to the pot and cover with water - then add enough water to double the volume. Add a half dozen peppercorns, a couple whole parsley sprigs (don't use dried), and a small piece (about an inch) of a fresh thyme sprig (ir 1/8 tsp dried).
Bring to a simmer, skimming any foam that develops, then partially cover and simmer a couple or 3 hours, making sure the liquid level does not go below the top of the bones.
Strain all the solids out. Taste. If flavorful enough, fine, it's done. If not, return to the stove and simmer, uncovered, till the stock has reduced and is more flavorful. Season to taste, as desired.
