Rinse salmon under cold running water, dry, cut diagonally into very thin slices and arrange on the spot on well-chilled serving plates.
Sprinkle with coarse salt and white pepper, drizzle with lime juice and oil. Mix crème fraîche with sour cream and caviar.
Place a spoonful of caviar cream on the center of each unit of salmon form and garnish with finely chopped lettuce leaves.