Soak bread in water. Peel and finely chop the onions. Knead minced meat, half of the onions, squeezed bread, parsley, curd cheese, mustard, salt and pepper. Form small balls from the minced mass.
Clean the zucchini (cut off the ends). Cut the zucchini into slices. Clean, wash and cut the peppers into pieces. Clean the mushrooms, possibly wash and cut in half. Clean, wash and cut tomatoes into pieces.
Wash parsley, dab dry and chop finely. Let the puff pastry thaw at room temperature. Heat the oil in a large pan and fry the meatballs for 3-4 minutes, turning them over at medium heat.
Remove from the pan and set aside. Add the mushrooms, peppers, the rest of the onions and zucchini to the frying fat and fry for approx. 6 minutes, turning over. 2 minutes before the end of the frying time, add tomatoes, peas and 3/4 of the parsley.
Season to taste with salt and pepper. Add meatballs. Separate egg. Whisk the egg white with a fork. Grease 4 small ovenproof tartlets and brush with egg white. Halve the puff pastry slices.
Roll out each panel to a square (approx. 16x16 cm) on a floured work surface. Cut a small hole in the middle of each plate. Distribute the vegetables with meatballs in the moulds. Place one puff pastry sheet on each and press the edge firmly.
Bake in the preheated oven (electric oven: 200 °C/ gas: level 3) for 20-25 minutes. In the meantime whisk the egg yolk and cream. Approx. 5 minutes before the end of the baking time brush the puff pastry with it. Remove from the oven and sprinkle with remaining parsley.
Serve garnished with marjoram as desired.