Let the puff pastry thaw. For the filling, chop the ham, onion and parsley very finely. Mix with the crème fraîche, the egg white and freshly grated Gouda cheese. Season with pepper, oregano and salt.
Cut the dough into five parts and roll them out into a rectangle (15 x 35 cm). Spread the filling and roll it up from the long side. Cut the rolls into 2 - 3 cm thick slices and place them on a cold-rinsed tray. Brush the sides with whisked egg yolk.