Preheat the oven to 400℉. Generously grease a 6 hole donut pan with vegetable oil.
In a medium sized bowl mix the dry ingredients - almond flour, oat flour, potato starch, cane sugar, baking powder, baking soda and sea salt. Stir until there are no clumps.
In a small bowl or measuring cup mix the wet ingredients - almond milk, club soda, oil, vanilla extract and lemon zest. Pour the wet ingredients into the dry and stir until just mixed. The batter should be quite moist and slightly lumpy. Be careful not to over mix.
Spoon or pipe the batter into the donut pan. Push about 5-6 blueberries into each donut. Smooth out the top of the batter.
Bake for 15 minutes, until a knife inserted comes out clean. Let them cool in the pan for 15 minutes. Remove from the pan onto a cooling rack. If the donuts stick gently use a butter knife to loosen the donuts from the pan. While the donuts cool start on the blueberry sauce.
Blueberry Sauce
In a small pot add the blueberries and water. On medium heat bring to a boil. Turn to medium low. The mixture should be lightly bubbling. Let it cook for 5 minutes. It's done when the blueberries become soft and start to burst. Make sure not to cook it too long or too much of the water will evaporate.
While the mixture is still warm, strain it in through a fine mesh strainer, pressing the blueberries with the back of a spoon so that all of the juices are released. You should have almost 1/2 cup of smooth blueberry sauce.
Icing
Add the icing sugar into a small bowl that is wide enough to dip a donut. Add the strained blueberry sauce one tablespoon at a time. Whisk until the icing is smooth. If you want a thin glaze add more blueberry sauce. I used 5 tablespoons for a thick icing.
Dip the cooled donuts into the icing and place back onto the cooling rack. Top the donuts with fresh blueberries and mint. The donuts are best eaten the same day. The texture of the donuts becomes more dry and crumbly the next day. Enjoy!
Notes
*Frozen blueberries can be used for the donuts and the sauce, although fresh is preferred. For the donut batter, dust the frozen blueberries in a bit of cornstarch before placing them into the batter. For the sauce no changes need to be made, follow the recipe the same using frozen blueberries.