Preheat the oven to 350 degrees F. Line muffin cups with muffin liners or spray with nonstick cooking spray.
In a medium bowl, stir together the bananas, sugars, butter, milk, and egg; set aside.
In another medium bowl, whisk together the flour, instant espresso powder, baking soda and salt. Make a well in the middle of the dry ingredients. Pour the wet ingredients into the well and stir just until combined. Fold in the chocolate chips.
Fill each cup about 3/4 full. Bake in the center of the oven for 20-25 minutes, until a toothpick inserted in the center of the muffin comes out clean.
Move the muffin pan to a cooling rack, and let cool for 15 minutes. After 15 minutes, remove the muffins from the pan and let them finish cooling on the cooling rack.