1. Preheat the oven to 180 °C. Line a baking pan with baking paper. Place the nuts in a food processer and blitz until finely ground. Add the flour, icing sugar and cinnamon to the food processor and blitz. Add the butter until everything is combined or use your fingertips to mix all the ingredients together.
2. Press the mixture into the lined baking pan, making it even, and freeze for 30 minutes. Remove from the freezer and bake for 20 minutes.