(*) Preheat oven to 190 °C in time for 8 pockets or 16 croissants.
Mix salmon, cucumber and radish with crème fraîche to a loose mixture. Season with sugar, salt, juice of one lemon and a little bit of pepper.
Cut the puff pastry slices in half. Put a tablespoon of the salmon mixture on each, brush the edges with egg yolk and fold into a triangle.
Brush pockets with egg yolk, sprinkle with sesame seeds and place on a baking sheet lined with parchment paper.
Bake in a heated oven at 190 degrees for about 15 min until golden brown and bring to the table.
Cut equal triangles, top each with a teaspoon of salmon mixture and roll up into croissants.