Roll out the puff pastry and cut it in half lengthways to make two long rectangles.
For the filling, finely chop the ham, peeled shallot and parsley. Mix everything together with Gouda, sour cream and egg white. Season with salt, pepper and oregano.
Spread the filling on the puff pastry sheets. Leave the edges free and moisten with a little water if necessary. Roll up the puff pastry from the long side and press the edges well. Cut the roll into finger-thick slices with a sharp knife and place the cut side on a baking sheet lined with baking paper.
Tip: moisten the knife with water to prevent the dough from sticking to it.
Brush the rolls with whisked egg yolk and bake in a preheated oven at 160 ° C on the middle rack for 15 to 20 minutes until golden yellow.
A fine snack for parties, buffets, etc. Tastes very good, even lukewarm.
The filling can also be prepared the day before, but you should only mix the onion into the mixture on the day of preparation.