Preheat your oven to 350 degrees, and spray a standard size 12 cup muffin tin with non-stick spray. Place really ripe bananas in a large mixing bowl, and mash them "silly" with a fork. Add granulated and brown sugars, melted butter, milk, and then the egg. Stir the ingredients really well together until blended. (No need for a mixer; use a spoon!)
In a separate, large bowl, combine flour, baking soda, salt, and espresso powder. Whisk together. Create a well right in the middle of the dry ingredients, then pour in the banana mixture, and stir to combine. Next add the chocolate chips (I used mini chips), and fold them into the batter, only until ingredients are combined.
Divide the muffin batter equally between prepared muffin cups. The mixture should fill each cup about 3/4 of the way. Place muffins in preheated oven on the middle rack. Bake them for 20 to 25 minutes (oven temps very greatly- mine were ready at 22 minutes). Test their doneness by inserting a toothpick into center of muffin. If it comes out clean, the muffins are ready to remove from oven! The muffin tops should be golden brown in color. Once the muffins are out of the oven, let them cool for about 15 minutes (still in the muffin tin) on a wire rack. After 15 minutes, transfer muffins from the pan to the wire rack, and let them finish cooling down. Serve... and ENJOY!
TIP: If you don't have access to instant espresso powder, you can substitute 2 teaspoons of very finely ground dark roast coffee.