Grease a 6-inch round springform pan with non-stick cooking spray. Line the bottom with a parchment round and cut a long strip to line the inner sides of the pan.
Add blueberries, eggs, yolks and coconut sugar and blend until smooth, scraping down the sides of the blender as needed. You want to blend for a few minutes to fully blend the blueberry skin and seeds. Working quickly, add in the cocoa powder and blend until smooth and uniform in color. There should not be any visible blueberry skin or seeds.
Transfer the batter into the prepared cake pan and try your best to smooth the top with a spatula. Bake for 55-65 minutes or until completely set. The cake will be very dark in color because of the blueberries, which turn the batter dark when they oxidize.
Let the cake cool completely before releasing it from the cake pan. This cake is very moist and fudgy. I recommend letting the cake set for several hours before removing. You can also place it into the fridge for a few hours to help it set more firm and to help the flavors develop better. If desired, frost cake before serving (optional frosting recipe provided in the recipe notes). Store uneaten leftover cake in an airtight container in the fridge or freezer.
Notes
Blueberry note: This recipe works best with fresh blueberries. Frozen blueberries may make the batter too wet. I also recommend using sweet blueberries if possible, otherwise the cake may not be sweet enough.
Cocoa powder: This recipe works best with Dutch process cocoa powder. Natural cocoa powder is too bitter. I use Rodelle cocoa powder.
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This recipe uses 2 eggs plus two additional egg yolks. Do not use 4 eggs because it will make the cake too eggy.
Optional chocolate frosting:
½ cup dark chocolate chips
¼ cup (2 ounces) canned coconut milk (can substitute with heavy cream if you don't need dairy-free)
Add chocolate chips to a medium bowl and set aside. Heat coconut milk in a small pot or pan over medium low heat. Heat until simmering. Pour hot coconut milk over chocolate chips. Let sit for 60 seconds then gently mix until chocolate is completely melted. Frost over surface of the cake.
You can make 1.5 times the frosting if you desire a thicker layer of frosting.
Estimated nutrition does not include optional frosting.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.