Banana Espresso Chocolate Chip Muffins

I started baking these muffins about a year ago when I bought the "Baked" cook book. This is the same cook book I got the chocolate chip cookie recipe from, so you know it has to be good! I love the combination of banana and chocolate and I love muffins. They are the best little snack when you are craving a delicious baked good. This is my cousin Rachel's favorite dessert that I make so every time I make them she calls dibs on at least half the batch! :)
Here is the recipe:
1 1/2 cups mashed, very ripe bananas (about 4 medium bananas)
1/2 cup sugar
1/4 cup firmly packed light brown sugar
1/2 cup unsalted butter, melted
1/4 cup whole milk (i use lactose free low fat milk)
1 large egg
1 1/2 cups all purpose flour
1 teaspoon instant espresso powder
1 1/2 teaspoons baking soda
1 teaspoon salt
1 cup semi sweet chocolate chips
Preheat oven to 350 degrees. Spray a 12- cup muffin pan with non stick cooking spray or you can use paper muffin liners in the pan.
In a medium bowl, stir together the bananas, sugars, butter, milk, and egg.
In another large 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 until just 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 tooth pick inserted in the center of a muffin comes out clean. Move the muffin pan to a cooling rack, and let cool 15 minutes. Remove the muffins from the pan and let them finish cooling on the cooling rack.
Muffins can be stored in an airtight container for up to 2 days.