Makes 2 Quarts
Preheat Oven to 400°
Place the bones (in a single layer), and the onions in a large roasting pan. If you add the veal trimmings, scatter them around the bones. Using a spatula cover the bones with the tomato paste. Roast in oven 1 or 2 hours or until bones are golden brown on all sides. Remove roasting pan from oven and place browned bones in a large stock pot (16 to 24 quarts).
Add all remaining ingredients and add enough cold water to cover at least by 2 inches. Bring to a boil, then reduce the heat so that mixture just bubbles at a gentle simmer and let cook for at least 5 hours, better overnight. Turn off the heat and let the stock cool down for one hour so that it's easier to handle.
When the stock has cooled a bit, use a slotted spoon or tongs to remove the bones and cooked vegetables and discard. Strain the stock through a very fine sieve to remove any small particles. Don't worry about removing the fat floating on top of the stock. It's easy to remove when it is real cold.
Refrigerate overnight and the next day remove ALL visible and congealed fat.
Portion the stock into containers ‑‑ from ice cube trays to pint size.
Label and date containers, then freeze for many many months.