In a small saucepan, heat the 300ml milk until it is steaming. Turn off the heat, add the butter and leave to melt.
In a large bowl, combine the 500g flour, salt, 75g sugar, yeast, baking powder and xantham gum. Once the milk has cooled until it's lukewarm, pour it into the flour mixture with the egg and stir until it comes together.
Lightly oil a large bowl and place the dough in it. Cover with clingfilm and leave to rise for an hour or until almost doubled in size.
Mix the currants, mixed peel, spices, grated apple and orange zest into the dough with your hands. Divide this into 9 and space out in a large, square tin. Cover with clingfilm and leave to prove in a warm area for around an hour or until puffed up.
Meanwhile, preheat the oven to 180°C/160°C fan/gas mark 4. Combine the extra 3 tbsp gluten-free flour with 4 tbsp of the extra milk and place in a piping bag. Set aside.
Once the buns have proved, pipe the flour mixture over them in crosses and bake for 15 minutes. Combine the extra 2 tbsp milk with the extra 2 tsp sugar and brush this over the buns. Return to the oven for 15-20 minutes or until golden. Remove from the tray and leave to cool.
Meanwhile, warm the apricot jam in a small saucepan with a splash of water. Brush this over the buns and serve.