For the Zwickerbusserl, prepare the shortcrust pastry (flour, butter, sugar, egg yolks, pinch of salt and lemon zest) and place in plastic wrap to rest in the refrigerator for about 1 hour.
Preheat the oven to 150 °C, roll out the short pastry, cut out round cookies and place on a baking tray. Make sure to cut out the same number of cookie bottoms and cookie parts that will receive a meringue topping.
Beat the egg whites with a pinch of salt until they turn white, then add the sugar and continue beating until the snow is stiff and forms beautiful peaks.
Use a piping bag to pipe the snow onto the cut-out cookies – start at the cookie, press on some of the mixture and pull the piping bag upwards until a tip forms.
Bake in the oven, making sure the snow does not turn brown. When cool, glue together one cookie part without jam and one cookie part with meringue topping with jam.