Using the whisk on a hand mixer, beat the butter, salt, gingerbread spice and sugar until light and creamy. Mix in the muesli, flour and water. With damp hands, shape the mixture into approx. 20 balls, flatten a little and place on a baking tray lined with baking paper.
Approx. 15 mins. in the centre of an oven preheated to 200°C. Remove from the oven, allow to cool slightly, then leave to cool completely on a rack.