In the mug, mug the egg yolk, milk, vanilla extract together until combined. Add in the almond flour, protein powder, baking powder, and mix to combine. Gently fold in the chocolate chips and bake on high in the microwave for 30-45 seconds.
Top your mug cake with a few more chocolate chips or peanut butter and enjoy! Be careful the mug will be hot when you mull it out of the microwave.