Mix together the butter, brown sugar and white sugar until smooth.
Add the beaten egg and sherry to the mix.
Stir the flour and baking powder together and add to the mix. Combine well together.
Mix in the white chocolate chips and cranberries.
Line a baking tray with tin foil. Mould the cookie mixture into small balls and place on the tray, flattening with your hand. Make sure to leave some space between the cookies as they will expand as they cook. You can make them as big or small as you like.
Bake for about 15 minutes, keeping a close eye on them to ensure they don’t burn. It’s nice if they stay a bit moist and chewy.
Remove from the oven and leave to cool for about 10 minutes before moving them from the baking tray.