In a bowl, rub together the flour, xanthan gum if using, salt and butter with your fingertips to form breadcrumbs
Add the sugar and knead into a dough, adding a few drops cold water as required to help it come together
Knead in the nuts and cranberries then form a sausage shape from the dough about 4cm in diameter
Wrap in clingfilm and chill for half an hour
Preheat the oven to gas 4 / 180C / 350°F and line a baking tray
Cut the dough into 24 pieces and roll into balls, then flatten with the palm of your hand. I find it easiest to cut the dough into quarters then mark with a knife 6 lines on each quarter sausage then cut through into even slices
Place on the baking tray and bake for 14 - 18 minutes until slightly golden
Let sit on the baking tray a couple of minutes before cooling completely on a wire rack then dust lightly with icing sugar
You can freeze half of the dough for later use if required. It'll keep for around 3 months
You can leave out the pistachios if you can't tolerate nuts or exchange them for sunflower seeds
