Preheat your oven to 350 degrees F. Line 12 muffin cups with foil (not paper) liners and grease the liners.
In a large bowl, whisk the eggs. One by one, whisk in the butter, stevia, vanilla, and milk.
Whisk in the coconut flour, then the cocoa powder. Finally, whisk in the kosher salt and baking soda.
Using a 4-tablespoon scoop, divide the batter evenly among the prepared muffin cups.
Bake until set and a toothpick inserted in center comes out clean, 18-20 minutes.
Cool the muffins for 10 minutes in the pan on a cooling rack, then cool them directly on the cooling rack until completely cool, about 30 more minutes. The muffins taste much better when they've had a chance to cool and set.
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Notes
*Occasionally, baking soda can cause a reaction in baked goods that results in an unpleasant ammonia smell. If you're concerned about it happening, you could use 4 teaspoons of gluten-free baking powder instead of baking soda. Make sure the baking powder is fresh and not expired. Since coconut flour is so absorbent, it's best to measure it by weight and not by volume. Each additional tablespoon makes a big difference, so it's best to be as accurate as possible.If using Dutch-processed cocoa powder, substitute 4 teaspoons of baking powder (gluten-free if needed) for the 1 teaspoon of baking soda.You can experiment with using a granulated sweetener instead of stevia if you wish, possibly increasing the amount of liquid you add to the batter.Leftovers keep well in an airtight container in the fridge for up to a week. Warm them briefly in the microwave prior to serving (after removing the foil liners, of course).