Pre-heat oven to 220°C / 200°C fan assisted / gas mark 7 / 425°F. Line a 12 hole regular sized muffin tin with muffin cases.
Prepare streusel topping first by whisking together the sorghum flour, almond flour, cassava flour, brown sugar and salt in a bowl.
Add the softened butter in and rub together with your fingertips until you create a sandy texture. Set aside whilst you prepare the main muffin mixture.
In a large mixing bowl, whisk together the sorghum flour, almond flour, cassava flour, baking powder, bicarbonate of soda and salt. Reserve 2 teaspoons for mixing with the blueberries.
In a separate bowl, whisk together the sugars, eggs, Greek yoghurt, melted butter and vanilla extract.
Pour the wet ingredients into the dry ingredients and stir until well combined.
Pour the blueberries into a smaller mixing bowl and remove a small handful for dotting on the top of the muffins.
Sprinkle in the 2 teaspoons of reserved flour mix and toss together so the blueberries are coated in flour.
Stir the rest of the blueberries into the batter.
Divide the muffin batter evenly into the prepared muffin cases.
Dot in the remaining blueberries so there’s 1-2 in the top of each muffin.
Scatter the streusel topping equally over the top of each muffin.
Place the muffins in the oven and bake at the high temperature for 5 minutes. Turn oven down to 180°C / 160°C fan assisted / gas mark 4 / 350°F and bake for a further 20 minutes.
Once baked, immediately remove the muffins from the tin and allow to cool on a wire rack completely.