This isn't a recipe--it's a way of life. Exaggeration? Possibly. But the next time a few cubes of flexible frozen stock saves your dinner, thank yourself for planning ahead.
Brown some bones. Five or six pounds of veal bones, say, to be purposefully inexact. Got a bunch of chicken bones? Those'll work too. Improvise. Put the bones in a very hot oven (400 to 500 degrees). Wait until they're very brown and caramelized. Leave them longer than you think you need to. Save the pan drippings.
While that's happening, make your mirepoix, posh kitchen talk for chopped vegetables. For six pounds of bone, you'll want about two pounds of mirepoix in a rough ratio of half onions and a quarter each of carrots and celery. Tiny pieces get mushy and murky while they cook, so chop your veg into decent sized chunks. Now cook the mirepoix in a cast-iron pan with a little oil over high heat until it's nice and glossy. Add a biggish dollop of tomato paste, if you like, for some added depth and sweetness.
Get it into a big pot with some bouquet garni. Tie together a bunch of parsley, a bunch of thyme and one big, fresh bay leaf. Now add everything (including the pan drippings) to a weighty, tall, narrow stockpot. Add enough water to cover it and bring to a low simmer. Once the bubbles start to rise with some regularity, move the pot over so it's only half on the fire. Every half hour or so, remove the ickiness that collects around the side of the pot with a large spoon. You do not want the stock to boil, so be patient. Keep at it for a long time. We'd say six hours, but your mileage may vary.
Time to strain the solids out. Put the liquid into a new pot and reduce over medium heat until the stock is thick and coats the back of a spoon. At this point, the stock can be cooled and put in the fridge. Or frozen into cubes to be tossed into sauces and dishes like the suave stock master you have just become.