Add sugars and melted butter to a bowl and mix to combine.

Add egg, peanut butter and vanilla and mix until smooth using an electric whisk.

Add gluten free flour, baking powder, salt and optional xanthan gum, whisking with an electric whisk until smooth.

Place cookie batter in the freezer for 40 minutes, covering the bowl with cling film or place in tin foil if you need space.

Roll the dough into 13 balls (each weighing about 40g each / 2 tbsp).

Press each ball down gently to form a cookie and smooth the edges with your fingers.

Push a few small pieces of peanuts into the top of each. Option to sprinkle with a little sugar if you like a crispier outside.

Place cookies on the baking trays (leaving a gap between each so they can spread) and bake in the oven for about 10 - 12 minutes.

Remove from the oven and allow to cool on the baking tray. Transfer to a cooling rack to fully cool.