Add the grated cheese, double crème and the finely diced onion and stir everything very well until a homogeneous mixture is formed. You can also squeeze a clove of garlic. Season everything with pepper, salt and nutmeg and mix well again.
Roll out the puff pastry and cut into 4 rectangles. Distribute the spinach mixture on the dough rectangles, making sure that the mixture is only in the middle of the dough rectangles. Then fold the dough rectangles together so that the mixture is completely enclosed. Forming small squares is the best solution. Place the squares on a baking sheet lined with baking paper.
Put the egg yolks in a cup, add 2 tablespoons of cream and stir. Brush the dough squares with it and bake in the oven for about 20-25 minutes until golden brown.