In a small bowl, combine butter, garlic, pepper and salt. Brush pitas with garlic butter. Grill pitas on hot grill for 20-30 seconds per side or until lightly browned. Cut into quarters and set aside.
For the garlic aioli, in a small bowl combine mayonnaise, lemon juice and zest, remaining garlic, mustard and dill. Stir until smooth.
Transfer remaining garlic butter to a medium skillet. Pre-heat over medium heat until hot. Add asparagus and shrimp. Cook for 3-4 minutes or until shrimp is cooked through and asparagus is crisp tender.
To assemble, fold each cheese slice and place on each pita quarter. Top with shrimp and asparagus mixture. Drizzle aoli on top and garnish with dill, lemon zest and black pepper.