Preheat the oven to 350 degrees F.
Add the muffins (foil or liner) and spray the muffins pan muffin liner and set aside.
In a bowl, whisk the dry ingredients; flour, baking powder, sugar, and salt. Set aside.
In another bowl, mash the ripe banana.
Add one egg to the mashed bananas and mix lightly.
Combine the mashed banana with the butter mixture to the flour.
Add the milk to the mixture (banana and flour) and combine. Don't overmix, no one wants touch muffins.
Gently mix the chocolate into the mixture.
DIvide the banana batter among the muffins pan, don't overfill the pan.
Bake in the preheated for about 25-30 minutes or until you insert a toothpick in the center and comes out clean.
Let the muffins rest before removing them from the pan.