Preheat the oven to 180C/350F. Line a large baking sheet with parchment paper and set aside.
In a large mixing bowl, add your coconut flour, almond flour, 3 tablespoons of sweetener, and baking powder, and mix well. In a separate bowl, whisk together the heavy cream, coconut oil, one egg, and one egg yolk, vanilla extract, until combined. Gently fold through the dry ingredients into the wet ingredients until combined. Fold through the blueberries. Gently knead the dough until mostly smooth.
Lightly dust a flat surface with almond flour. Transfer the dough onto it and gently knead into a ball. If the dough is too sticky, add a little extra almond flour. If the dough is too thick, add some heavy cream or milk. Press down and flatten into a thick disk. Using a sharp knife, cut 8-10 triangles.
Place the scones onto the lined sheet. Brush the tops with the egg white and sprinkle the remaining tablespoon of granulated sweetener over the top. Bake for 20-25 minutes, or until golden around the edges.
Remove from the oven and let cool completely.
* One whole egg and egg yolk is used in the dough. The remaining egg white is used to brush the tops before baking. TO STORE: Leftover scones should be stored in the refrigerator, completely covered. They will keep well for up to 1 week. Any longer and the blueberries will blend into them and will become soggy. TO FREEZE: Place scones in ziplock bags and store them in the freezer for up to 6 months.