Preheat and prep: Set your oven to 350°F (175°C).
Line a 12-cup muffin tin with paper liners or lightly grease with butter or coconut oil.
Mix dry ingredients: In a large bowl, whisk almond flour, coconut flour, baking powder, salt, and sweetener until no lumps remain.
Whisk wet ingredients: In a separate bowl (or the same, after pushing dry mix to the sides), whisk eggs, almond milk, sour cream, melted butter, and vanilla until smooth.
Combine: Pour wet into dry and stir gently with a spatula until just combined. The batter will be thick but scoopable. If it’s too stiff, add 1–2 tablespoons more almond milk.
Fold in chips: Stir in the chocolate chips (and nuts, if using).
Don’t overmix.
Portion: Divide batter evenly among the muffin cups, filling each about 3/4 full. Press a few extra chips on top for looks.
Bake: Bake 16–20 minutes, or until the tops are set and a toothpick comes out clean or with a few moist crumbs.
Cool: Let muffins cool in the pan for 5 minutes, then move to a rack. Allow to cool at least 15 minutes before eating to set the crumb.