Preheat oven to 325F/165C/gas mark 3. Line two muffin tins with paper cupcake liners or use silicone muffin cups.

Sift and measure the flours into a large bowl. Whisk or sift all the dry ingredients together (the sorghum flour through the baking soda).

Wash and thoroughly drain the blueberries, removing any stems and spoiled berries. Sprinkle a large spoonful of the flour mixture over the berries, and mix until all the berries are coated. This will keep the berries from sinking down into the batter and should help keep them from staining the batter.

Add the ground flax seeds to 6 tbsp (90 ml) filtered water in a large mixing bowl (the bowl for a stand mixer if you have one) and let it stand five minutes.

Add the agave syrup, vegan sour cream, vanilla extract, and lemon zest to the mixer bowl and blend for 3 minutes. You want to add as much air as possible to help create a tender, fluffy muffins. Turn off the mixer in between each addition: add in the flour mixture a bit at a time until it is thoroughly mixed. Add in the mineral water and mix just until you have a smooth, pourable cake batter.

Fold in the berries with a spatula just until evenly distributed.

Using a measuring cup or ice cream scoop, fill the cups no more than 2/3 full. Sprinkle each top lightly with coconut sugar.

Bake for 11 minutes. Turn the pans 180 degrees so they bake evenly. Bake another 8-11 minutes, or until the tops crack a little and a toothpick inserted into the center comes out clean.

Remove from the oven and set on wire racks to cool. When the pans are cool to the touch, remove the muffins and set on the wire racks to finish cooling completely.