Chop up the banana, briefly toast the hazelnuts in the pan and then knead with the rest of the ingredients to form a firm dough (if you briefly heat the margarine, kneading is easier).
Let this dough rest for about 10 minutes. Now roll out the dough and cut out cookies. Bake on the baking sheet in a preheated oven at 180 ° C for about 15 minutes.
After baking, the cookies should cool down a little to become harder. The dough is enough for about two baking trays, but that depends on the thickness when rolling out.