Preheat oven to 375 degrees F (190 degrees C). Lightly grease 12 muffin cups, or line with muffin papers.
In a large bowl, mix together 1 1/2 cups flour, baking soda, baking powder, cocoa and salt. In another bowl, beat together bananas, sugar, egg, vanilla and melted butter.
Stir the banana mixture into the flour mixture just until moistened.
Add chocolate chips.
Spoon batter into prepared muffin cups.
Bake in preheated oven for 15-17 minutes, until a toothpick inserted into center of a muffin comes out clean.