For the Hussarenkrapferl, cream butter in a food processor until fluffy, gradually adding sugar and yolks.
Then add flour. Form small balls from the mixture, brush with beaten egg, sprinkle with hazelnuts and place on a baking tray lined with baking paper.
Using the handle end of a wooden spoon, press each ball down hard in the center. Bake at 180 °C until light yellow and when cool, fill the Hussarenkrapferl with smoothly stirred jam.