In a small bowl, combine the psyllium husk with 2/3 cup of warm water. Leave to stand for about a minute until it has formed a gel.
In the bowl of your stand mixer, whisk together the gluten free bread flour blend, sugar, gluten free baking powder, instant yeast, salt and xanthan gum, if using. Make a well in the middle and add the beaten egg, melted butter, 1/2 cup + 2 tbsp more of warm water and the psyllium gel. Bring everything together into a rough dough using first a fork, then your hands.
With the dough hook fitted, knead the dough in the stand mixer for 5 minutes until smooth.
Meanwhile, make the filling by beating together then soft butter, brown sugar and cinnamon until smooth.
Roll the dough out into a 12 x 16 inch rectangle on a lightly floured surface. Spread evenly with the butter and cinnamon mixture, then using a very sharp knife slice into 10 long 1 1/2 inch strips.
Butter a large baking dish (round or rectangle, you just want to be able to fit in all the rolls only just touching in a single layer) and roll up each cinnamon roll, arranging them in the dish.
Cover with food wrap and leave to rise for 1 1/2 hours. When ready to bake, the cinnamon rolls should appear puffed and doubled in size.
With 1/2 hour to go, preheat the oven to 335F. Cover the proofed cinnamon rolls loosely with tin foil and bake for 30 minutes. Then, remove the foil and bake for a further 10-15 minutes until golden.
Allow to cool in the pan before combining the powdered sugar, vanilla and 2 tbsp of water together to make a glaze you can drizzle over 5 minutes before serving.