Pre-heat your oven to 160°C/140°C fan/Gas 3.
If your walnuts are not already toasted, simply place them in a dry saucepan (e.g. no oil) and heat for 2-3 minutes until they start to darken and release their nutty aroma.
Put the toasted walnuts into a blender and blitz on high until they have formed a powder.
In a small bowl, cream together the butter and the icing sugar.
Stir in the toasted walnuts followed by the flour and baking powder.
Mix until the ingredients are all well incorporated and a stiff dough has formed.
Wrap the ball of dough in cling film and chill in the fridge for 15-30 minutes or until it is firm enough to roll out.
Roll the dough out on to a lightly floured surface until between 0.5 and 1cm thick.
Cut out your biscuits using a cookie cutter of your choosing and place on to a baking sheet.
Place the baking sheet back in the fridge to cool for another 10 minutes (or in the freezer for 5 minutes)
Once chilled, bake for 20 minutes or until they are just turning golden.
Leave to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.
Once cooled, melt your chocolate gently either in the microwave for 15 second intervals, and stirring each time or over a bain marie.
Dip the biscuits in the chocolate and decorate with gold leaf or sprinkles if you wish.