Preheat the oven to gas mark 4 or 180 degrees Celsius.
In a large bowl, mix together the butter, flour, baking powder and xanthan gum and rub between your fingers to form breadcrumbs.
Mix in the beaten egg (leave a drizzle for later) and add the cheese to form a dough, again leave a tablespoon of cheese for later.
Roll out the dough on a floured surface until 1cm thick and cut into straw-like rectangles.
Place on a lined baking tray, brush with the leftover beaten egg (add a little water if there's only a small amount) sprinkle with a little extra grated cheese, and bake for 15 minutes.
Leave to cool before serving.