Cut the celery, carrots, and onion coarsely. Fry in butter till browned. Lightly crush the peppercorns.

Add flour and and make a roux. Heat the beef stock in another pot. When the roux is browned about 6 minutes, add the tomato paste, garlic, broth, and bay leaf. Whisk so the roux won't lump up. Add in the peppercorns.

Simmer and allow to reduce for 45 minutes. When reduced strain through a sieve. Discard the solids. Done let cool. You have just made a mother sauce!!!