and finely chopped In a large saucepot place the beef shank. Add enough water to cover it completely. Bring the water to a boil over high heat. Skim off any foam that rises to the top. Add the onion, carrot, bouquet garni, salt, and pepper. Reduce the heat to low and simmer the beef for 6 to 8 hours, or until it is very tender. Remove the bone from the beef shank and discard it. Return the meat to the liquid and let it cool. Slice the beef into eight 1 cm thick medallions. Brush the medallions with the olive oil. Grill them for 2 to 3 minutes on each side, or until they are nicely browned and heated through. On each of 4 individual serving plates place 2 of the medallions and 2 of the steamed baby leeks. Place the Gribiche Sauce next to them. Gribiche Sauce: In a medium bowl place the Dijon mustard and the red wine vinegar. Whisk them together so that they are well blended. While whisking constantly, slowly dribble in the oil. Add the remainder of the ingredients and whisk them in.