Into a large mixing bowl whisk together the buckwheat flour, brown rice flour, sorghum flour, potato starch, tapioca starch, oat flour, sugars, beet powder and salt.
In a medium bowl whisk together the levain, water, milk, psyllium husk, flax seed, and food colouring until completely combined.
Pour the psyllium mixture into the middle of the flour blend and stir with a spoon to create a shaggy dough.
Place the dough on a work surface, knead and and shape the dough into a ball.
Let the dough rise for about an hour in a warm place and then cover and put in the fridge overnight to ferment. Alternatively, skip the fridge step, roll the dough out, add the filling and then let it rise for a few hours.
While the dough is rising prepare the filling.