Preheat the oven to 350 degrees. Place cupcake liners in your muffin pan.
Place bananas in a large bowl or the bowl of your stand mixer. Mix until well mashed. Add the butter or coconut oil and light brown sugar. Mix to combine them, then add the egg, milk and vanilla. Mix on a medium speed until combined as much as possible. The butter will likely still separate.
Combine the baking soda, salt, flour and cocoa powder in a small bowl. Add slowly to the wet ingredients on a low speed. Once all of the flour is mixed in, turn up the speed on the mixer and combine well.
Add in ½ cup of the chocolate chips by hand.
Spoon or scoop batter into cupcake liners. Sprinkle remaining chocolate chips on top of the batter.
Bake for about 15-20 minutes. Watch them closely after 15 minutes. They might be done at this point. Once the top is solid and the center doesn’t jiggle, take them out and let them cool for at least 10 minutes before removing the liners from the cupcakes. Taking them out of the liners before they cool will result in them falling apart… super sad after you started drooling when you took them out of the oven;-)