Prep the pan: Preheat your oven to 350°F (175°C).
Lightly grease a 6-cavity donut pan with oil or nonstick spray. If using a silicone pan, still grease lightly.
Mix dry ingredients: In a large bowl, whisk almond flour, coconut flour, cocoa powder, sweetener, baking powder, baking soda, and salt to break up any clumps and create an even mixture.
Combine wet ingredients: In a separate bowl or measuring cup, whisk eggs, almond milk, oil, and vanilla until smooth and fully combined.
Bring it together: Pour the wet mixture into the dry ingredients. Stir with a spatula until just combined.
The batter will be thick but scoopable.
Fold in chips: Add sugar-free chocolate chips, if using, and fold gently to distribute evenly.
Fill the pan: Spoon or pipe the batter into the donut cavities, filling each about 3/4 full. Smooth the tops for even baking.
Bake: Bake for 14–18 minutes, or until the donuts are set and a toothpick inserted into one comes out with a few moist crumbs.
Cool: Let the donuts cool in the pan for 5–7 minutes, then carefully transfer to a rack to cool completely. Keto donuts firm up as they cool.
Make the glaze (optional): Melt the chocolate chips with coconut oil in a microwave-safe bowl in 20–30 second bursts, stirring in between, until silky.
Add a tiny pinch of salt.
Glaze and set: Dip the tops of the cooled donuts into the glaze, then place on the rack. Let the glaze set for 10–15 minutes before serving.