Cut the banana and butter into smaller pieces and put them into a mixing bowl. Beat well with a hand mixer. The mixture will appear grainy, but that's okay.

Now add an egg and vanilla sugar and beat everything well together. This takes about a minute.

Add the oatmeal and stir until it forms a homogeneous mass.

Add the wheat flour little by little until the dough reaches a consistency similar to shortcrust pastry.

Chill the dough for 30 minutes.

Roll out the dough on a floured surface to a thickness of about 1-2 millimeters.

Now it's just a matter of cutting out biscuits in your favorite shapes. Place them on baking sheets lined with baking paper.

Bake the biscuits for 10 minutes at the bottom of the oven at 200 degrees Celsius (392 degrees Fahrenheit) (convection).

Let the biscuits cool on a wire rack before storing them in a cookie tin.

The biscuits can be stored for about 14 days.