Preheat the oven to 180°C.
Mash the banana and chop the chocolate into small pieces.
In a bowl, combine the butter and sugar.
Add the egg and mix well.
Add the mashed banana and stir to combine.
Sift in the flour, baking powder, and salt, then mix.
Fold in the chocolate chips evenly.
Divide the batter into muffin molds.
Bake in a 180°C oven for 20 minutes.