Stir together first 5 ingredients.
Place shrimp in a large Dutch oven; pour Worcestershire sauce mixture over shrimp. Squeeze lemons over shrimp mixture; add squeezed lemon halves and 1/4 cup water. Bring to a boil over high heat, stirring frequently; cook, uncovered, 6 minutes or just until shrimp turn pink, stirring frequently. Remove from heat.
Gradually add butter, stirring until butter melts. Serve immediately with crusty French bread.
Bacco and Ralph Brennan Resturant Group