How to Make It
Preheat broiler. Place bread slices in a single layer on a baking sheet.
Broil bread slices until lightly browned, 1 to 2 minutes per side. Rub toasted bread with cut sides of garlic cloves.
Combine mayonnaise, mustard, and Old Bay in a small bowl.
Melt butter in a large skillet over medium-high; add sausage, and cook, stirring constantly, until browned, 3 to 4 minutes. Add shrimp to skillet; cook, stirring occasionally, just until shrimp turn pink, 3 to 4 minutes. Stir in parsley and salt.
Spread about 2 teaspoons mayonnaise mixture on one side of each toasted bread slice. Top each with about 1 tablespoon shrimp mixture.