For the spinach patties, sauté the finely chopped shallots in butter, add the defrosted and finely chopped spinach leaves and let them steam.
When everything has cooled down, add the remaining ingredients and mix well. Cut the puff pastry into even squares and fill each square with 1 tablespoon of the mixture. Shape into a pouch and brush the spinach patties with beaten egg yolk. Bake in the oven for about 20 minutes at 180°C until the patties are golden brown.