Martha Stewarts Shepherds Pie

Name: Martha Stewart's Shepherd's Pie
Ingredients: 3 tbsp. safflower oil; 3½ lb. lamb shanks; Coarse salt; Freshly ground pepper; 1 medium onion; 3 clove garlic; 2 tbsp. tomato paste; ½ c. dry red wine; 2½ c. homemade or store-bought low-sodium chicken stock; 1 dried bay leaf; 6 sprig thyme; 3 parsnips; 1 medium celery root; 4 oz. cipollini onions; 2 lb. Yukon gold potatoes; ¾ c. heavy cream; 4 oz. unsalted butter; 1¼ c. frozen peas