Wash the chard and remove it from the stalks (unfortunately the stalks are not used here). Cut the leaves into small pieces and cook in boiling water for 2-3 minutes until they collapse. Then drain and season with salt and pepper. Let cool down (important, otherwise the puff pastry will break).
Roll out the puff pastry on the baking sheet and place the cold chard on top so that there is still space on all sides. Season the salmon and place on the chard. First fold the puff pastry to the right and left towards the middle and then fold the other sides together in the middle and press down a little. Brush with the beaten egg and place in the oven preheated to 180 degrees for 30 minutes.