Season the meat with salt and pepper. In a casserole, heat the oil and sear the meat, a few pieces at a time, removing them from the pan when they are brown. Deglaze the pan with the red wine. Next add the lamb with the beef broth, onions, celery and herbs. Cover and cook in a 300-degree oven for 2 hours.
Remove from the oven and discard the large pieces of onion, celery and herbs. Shred the meat. Strain the broth, return to the casserole, and bring to a boil.
Slowly whisk the cornstarch mixture into the boiling liquid and stir until it thickens. Add the lamb, carrots and peas. Transfer to an ovenproof dish and top with a layer of mashed potatoes. Return to the oven for 15 minutes or until the liquid is boiling and the potatoes are crisp and brown. You may have to put the potatoes under the broiler to brown them.
Makes 6 to 8 servings
GARLIC MASHED POTATOES:
Wrap the garlic in foil and bake in a 400-degree oven for 40 minutes. Let cool and press the garlic out of the skins. Peel and cook the potatoes. In a bowl, mash the cooked potatoes, butter, cream and softened garlic. Season the potatoes with salt and pepper.