Preheat barbecue grill (oil hot grill to help prevent sticking).
Peel and devein the shrimp, leaving tails on. Using a sharp knife, butterfly shrimp by cutting along the inner curve or underbelly about halfway (almost completely through), leaving the tails firmly attached. Press the shrimp down flat like a butterfly. Place prepared shrimp in a shallow dish and sprinkle with olive oil; refrigerate, covered, until ready to cook.
In a medium bowl, combine white truffle oil, lemon juice, onion, and parsley. Season to taste with salt and pepper; set aside.
When ready to cook, season the shrimp lightly with salt and pepper. Place shrimp onto hot grill and cook approximately 2 minutes on one side; turn and cook another 1 minute or until shrimp are opaque in center (cut to test). Remove from grill.
To serve, arrange shrimp (split sides up) on a serving plate. Drizzle with a little of the vinaigrette. Place remaining vinaigrette in a small bowl and place on plate for dipping.
Makes 4 servings.
Grilled Shrimp With Truffle Oil Recipe: https://whatscookingamerica.net/shrimptruffle.htm