Preheat oven to 350 degrees. In a large skillet over high heat, heat half the peanut oil until it begins to smoke and sear veal shanks until they are brown on all sides. Remove shanks from the pan and set them aside. Lower heat to moderate and add the remaining peanut oil. When hot, put in the garlic, onion, mushroom caps and tarragon and cook, while stirring, until the onion is translucent. Add the tomatoes, vinegar and green peppercorns and cook until the liquid is reduced by half. Add the Teriyaki Sauce, water, mirin, chili and garlic paste, and brown sugar. Bring mixture to a boil. Return veal shanks to the skillet, cover, place in oven, and cook until the meat is fork tender, approximately 1- half hours. Skim any fat that accumulates on the surface of the braising sauce; add sesame oil to defatted sauce and serve. Serves 6 Teriyaki Sauce: 1 Tb. sesame seeds, toasted 1 cup soy sauce 1.5 ts. sesame oil half cup sugar 2 cloves garlic, minced 2 tsp. minced fresh ginger 1 cup thinly sliced scallions Place all ingredients in a small saucepan over moderate heat. Bring to a boil to allow the sugar to dissolve. Remove from heat and cool before using. Makes 1- quarter cups.