Roast bones on parchment covered cookie sheets at 425°F for an hour, turning and moving in oven every 20 minutes, until golden brown (do not char the bones)
Place onion in a 14-quart stockpot; add veal bones and scrape in all drippings from parchment paper, avoiding fat (use 2 pots if you don't have a large one)
Cover bones with water and bring to a simmer over medium high heat: skim, skim, skim
After simmered about 30 minutes and well skimmed, add remaining ingredients; mix well
Stir occasionally; skim as needed (much easier to skim before aromatics are added, so try to get that done well, during first 30 minutes)
Reduce heat to low as soon as coming to a simmer; partially cover pot, adjusting heat as needed to maintain gentle simmer: never boil
Simmer 8 hours longer
Cool stock in sink filled with cold water and ice cubes (I set mine in snow)
When cool, (next day, even) skim fat off surface; strain through a fine-mesh sieve into 2 smaller pots
Bring each to a simmer over medium-high heat and simmer for about 1 hour, or until reduced to 2 quarts
Strain again using fine sieve or cheese cloth over coarser sieve; cool to room temperature
Refrigerate, uncovered, until cold; cover and refrigerate for up to 1 week, or freeze in ice cube trays
Remove from trays, pack well into freezer ziplock bags and use as needed