Prep your pan: Preheat the oven to 350°F (175°C).
Line a 12-cup muffin tin with paper liners or grease well.
Mix the dry ingredients: In a large bowl, whisk together almond flour, coconut flour, sweetener, baking powder, baking soda, salt, and cinnamon until no lumps remain.
Combine the wet ingredients: In a separate bowl, whisk the eggs, melted butter, sour cream, vanilla, and almond milk until smooth.
Bring it together: Pour the wet mixture into the dry mixture. Stir gently with a spatula until just combined. The batter should be thick but scoopable.
If it’s too thick, add 1 tablespoon more almond milk.
Fold in chocolate chips: Gently stir in the sugar-free chocolate chips, reserving a small handful for the tops.
Fill the muffin cups: Divide the batter evenly among the 12 cups. Sprinkle a few extra chips on top for a bakery-style finish.
Bake: Place in the center of the oven and bake for 18–22 minutes, or until the tops are set and a toothpick comes out with just a few moist crumbs.
Cool: Let the muffins cool in the pan for 10 minutes, then transfer to a wire rack. They firm up as they cool, so avoid removing them too early.
Serve: Enjoy warm or at room temperature.
For extra decadence, add a small pat of butter while warm.