Melt butter in a saucepan over a low heat. Once melted, stir in the peanut butter. Then transfer to a bowl and set aside to cool.
Preheat oven to 200C/400F/gas mark 6.
Grease and line a square/rectangular baking tin roughly 20cm in size.
Sift together the gluten free flour, baking powder and salt in a large mixing bowl.
Stir the sugars into the cooled butter and peanut butter.
Next add in the eggs and vanilla vanilla extract.
Fold the wet ingredients gently into the flour. Then add the white chocolate and peanut butter chips.
Pour into the prepared tin and bake for 22-25 minutes, until just set.
Once cooled, cut into squares and serve.