Wash the walnuts and quarter them with a sharp knife. Be sure to wear rubber gloves when doing this.
Then pour into a large mason jar along with the other ingredients. Pour 1 liter of grain, vodka or fruit schnapps (the latter tastes best for me). Let stand in a sunny place for 6-8 weeks, then strain.
Let ripen in a dark place until winter, possibly sweeten with sugar syrup.