Thaw the puff pastry and roll it out on a lightly floured work surface about 2 millimeters thick. Then cut the rolled out puff pastry into rectangles and then into triangles.
Cut the salmon into thin strips. Grate the gouda. Mix the salmon, cheese, pine nuts and 2 egg yolks together.
Spread the filling over the puff pastry triangles. Then roll them up into croissants and place on a baking sheet lined with baking paper. Whisk the rest of the egg yolk and brush the croissants with it.
Bake at 200 ° (top and bottom heat) for about 18 minutes.