Cook the bacon until crisp, remove and drain. Saute the onions, carrots and garlic in the bacon fat until browned, about 10 minutes. Add the tomato paste and cook over low heat, stirring occasionally, for 5 minutes.
Stir in the flour and cook over low heat stirring constantly for 5 minutes. Add the wine, and cook over low heat for 30 minutes, or until reduced by half, stirring constantly near the end of the cooking time. Add the chicken and veal stock and simmer for 45 minutes.
Remove from the heat and strain through a china cap (fine meshed sieve) Mix the brandy and the cornstarch together thoroughly. Add to the sauce stirring until the sauce is thickened and smooth.. Stir in the butter. Preheat the oven to 375F.
Season the veal shanks with salt, pepper and oil. Bake for 15-20 minutes or until lightly browned. Place into large roasting pans and pour over sauce and cook partially covered, at 250F for 2-3 hours or until fork tender. Remove from heat and refrigerate. Store for up to 2 days. Reheat at 350F in sauce till hot