Preheat oven to 180c
In a large bowl, coming the flours and raising agents.
In a small bowl add the chia seeds and the boiling water and stir until it forms a gel.
In a separate bowl beat the butter and erythritol together, then add the chia mixture and beat again. Add the yogurt and beat.
With your mixer on low, add the dry ingredients to the wet in 3 parts, alternating until combined
transfer to a lined baking tin and bake for 25minutes.