New Orleans Barbecued Shrimp

1/4 cup vegetable oil1 medium onion, diced 1/2 cup chopped celery 1/2 cup red pepper, chopped2 cloves garlic, chopped2 pounds jumbo shrimp, peeled and deveined1 tablespoon lemon zest1 cup white wine1 tablespoon grainy mustard 1/4 cup Worcestershire sauce 1/2 cup coarsely grated black pepper8 tablespoons (1 stick) cold butter, cut into 1/2-inch piecesJuice of 1 lemon 1/4 cup chopped parsleyIn large sauté pan heat oil. Add onion, celery, red pepper and garlic and cook until translucent but still firm. Add shrimp and cook until pink. Remove shrimp to a plate and keep warm.To the pan add lemon peel, wine and mustard. Bring to a boil and simmer 3 minutes. Add Worcestershire sauce and black pepper; stir and simmer for 3 minutes.Melt butter into sauce one piece at a time, stirring until mixed well and sauce has thickened. Add back shrimp and lemon juice. Garnish with fresh parsley.Serves six.