Preheat your oven to a cozy 375°F (190°C).
In a spacious mixing bowl, whisk together the almond flour, coconut flour, protein powder, granular erythritol, baking powder, and salt until everything is well combined and fluffy.
Add the sour cream, eggs, and vanilla extract. Stir until you have a smooth, well-blended dough. If the dough feels a bit too wet, simply mix in an extra tablespoon of coconut flour. Gently fold in most of your fresh blueberries, saving a few for the tops. Let the dough rest for 5 minutes.
While the dough is resting, place 1 tablespoon of the butter into a 10-inch oven-safe skillet. Pop the skillet into the preheated oven to melt the butter.
Carefully remove the hot skillet from the oven. Lightly flour your hands (coconut flour works great!) and form the dough into approximate 2-inch balls. Arrange them in the hot skillet. Gently press any remaining blueberries onto the tops of your biscuits.
Melt the remaining 1 tablespoon of butter and drizzle it evenly over all the biscuits. Return the skillet to the oven and bake for 20 to 25 minutes, until your biscuits are wonderfully golden brown and feel firm when lightly touched.
Once baked, remove the skillet from the oven and let your healthy blueberry biscuits cool down for at least 20 minutes before serving.