Frogmore Stew with Shrimp and Andouille

In a large enameled cast-iron casserole, melt 1 teaspoon of the butter in the olive oil. Add the leek, celery and garlic and cook over low heat until softened, about 5 minutes. Add the tomatoes, lemon zest, thyme, parsley, corn, potatoes, fish stock, tomato juice and Old Bay seasoning and bring to a boil. Cover and simmer until the corn and potatoes are almost tender, about 5 minutes. Add the shrimp, sausage and lemon slices, cover and simmer until the shrimp are just cooked through, about 5 minutes. Remove from the heat, stir in the remaining 1 tablespoon of butter and season with salt and pepper. Ladle the stew into bowls, garnish with the watercress and serve with the grilled bread.