Bring water with butter and salt to a boil in a saucepan. Add the flour mixed with the cornstarch and stir. Keep stirring over low heat until the dough ball loosens from the pot and the bottom shows a white coating. Put the dumpling in a bowl and stir in the eggs one by one until the dough tears off the spoon in long tips. Then stir in the baking powder. Fill the incendiary material into a piping bag with a large nozzle. Squirt a ring onto a piece of greaseproof paper dipped in hot fat and hold the paper in the baking fat until the ring comes off the sheet. Spray on the next ring and bake in the same way.
Cover the ready-baked spritz cake with white icing or powdered sugar.