1. Preheat broiler to high.
2. Heat butter in a large nonstick skillet over medium-high heat; swirl to coat. Add shrimp to pan; sauté 4 minutes or until done. Place shrimp on a large plate; chill in refrigerator for 10 minutes. Coarsely chop shrimp. Combine chopped shrimp, mayonnaise, and next 6 ingredients (through salt) in a large bowl.
3. Open buns without completely splitting; arrange, cut sides up, on a baking sheet. Broil 1 minute or until toasted. Place 2 lettuce leaves in each bun; top each serving with 1/2 cup shrimp mixture.