Place the flours, xanthan gum, baking powder, bicarbonate of soda and butter in a food processor and whizz until the mixture resembles fine breadcrumbs. Alternatively, mix together the flours, xanthan gum, baking powder and bicarbonate of soda in a large bowl. Add the butter and rub in with the fingertips until the mixture resembles fine breadcrumbs. Stir in the sugar.
Mix together the egg and buttermilk in a separate bowl, add to the dry ingredients and mix to a soft dough.
Turn the dough out on a surface lightly dusted with rice flour, gently press out to a thickness of 2.5 cm (1 inch) and use a 5 cm (2 inch) cutter to stamp out 8 scones, rerolling the trimmings as necessary.
Put on a baking sheet lightly dusted with rice flour, brush with a little buttermilk and place in a preheated oven, 220°C (425°F), Gas Mark 7, for about 12 minutes until risen and golden. Remove from the oven and transfer to a wire rack to cool.
Whip the cream in a bowl until it forms fairly firm peaks and fold in the strawberries. Split the scones in half and fill with the strawberry cream.