2 pounds shrimp, small or medium, shelled and deveined
2/3 cup crème fraîche
3 tablespoons capers
Lettuce leaves
Lime slices, thinly sliced
1 tablespoon green onion tops, minced
Combine lime juice, green onions, salt and pepper in a medium bowl. Mix in shrimp. Cover and refrigerate until shrimp turn opaque, stirring occasionally, at least six hours. (Can be prepared one day ahead.)
Drain shrimp thoroughly, discarding marinade. Fold in crème fraiche and capers. Arrange lettuce on plates or scallop shells. Top with shrimp. Garnish with lime slices and green onions. Serve immediately.