To a large bowl add dairy free butter, light brown sugar and granulated sugar and whisk with an electric whisk until creamy.
Add the egg and continue to whisk. Add your vanilla extract and whisk again
Add the gluten free flour, baking powder, xanthan gum and salt. Mix well to form a dough.
Add the dairy free white chocolate buttons and the chopped pistachios. Place into the fridge for at-least an hour to chill.
Whilst the dough chills spoon 10 individual tablespoons (in circular shapes) of pistachio spread onto a tray topped with baking paper. Place in the freezer to set.
Preheat your oven to 180°C and line 3 large baking trays with baking paper.
Take your dough out of the fridge and the pistachio spread out of the freezer. The dough should be cold and the pistachio spread should be frozen. Take around 75/80g of cookie dough per cookie and flatten in your hands. Place the frozen circular pistachio spread in the middle of the cookie and wrap the cookie dough around the outside (so the spread is in the middle).
Continue to do for all 10 cookies. Place the cookies on your baking trays (they will spread so only place 3 or 4 cookies on each sheet). Bake in the oven for around 14 minutes. They will continue to cook and firm up once they are out the oven and cool.