Using an electric mixer, beat together the butter and icing sugar until soft, light and fluffy.
Sift in the flour, mixed Spice and baking powder. Mix until well combined.
Stir in the oats and cranberries. Bring the mixture together to form a dough.
Roll walnut sized pieces of dough in your hands.
Place them on the prepared baking tray. Flatten each one a little with the bottom of a glass. Use a small piece of baking parchment under the glass to help prevent it sticking to the dough.
Bake in the oven for around 15 mins or until lightly golden.
Take them out of the oven and dust with caster sugar.