Preheat oven to 375°F (190°C). Sauté shallot and garlic in 2 tbsp melted butter until soft, about 2 minutes, then cool slightly. Gently mix crab, panko, remaining butter, the cooled shallot mixture, lemon zest, 1 tbsp parsley, Old Bay, salt, and pepper.

Butterfly shrimp by cutting a deep slit along the back, leaving the tail intact, then press open and lay cut‑side up on a lined baking sheet.

Spoon about 2 tbsp crab filling onto each shrimp, pressing it gently into a mound.

Bake 15–18 minutes until stuffing is golden and shrimp are pink and opaque. Transfer to plates, spoon pan juices over, sprinkle with remaining parsley, and serve with lemon wedges.