In a large bowl, whisk together the flour, cocoa powder, granulated sugar, brown sugar, baking powder, baking soda, salt, espresso powder, and cinnamon.
In a medium bowl, stir together the mashed bananas, sour cream, eggs, oil, and vanilla. Gently fold the wet ingredients into the dry ingredients until just barely combined. Gently fold in the ¾ cup chocolate chips, being careful not to overmix.
Divide the batter evenly among the lined muffin tin cavities, filling each to ¾ full. Sprinkle about a teaspoon of mini chocolate chips onto the batter in each cavity.
Bake until a toothpick inserted into the center (avoiding chocolate chips) comes out clean, about 15 minutes. Let cool completely. Store in an airtight container for up to 3 days.