Preheat the oven to 350°F (175°C) and grease a loaf pan.
Mash bananas in a bowl until smooth.
Stir in melted butter, brown sugar, eggs, vanilla, and brewed espresso.
Whisk together flour, baking soda, salt, and cinnamon in a separate bowl.
Slowly fold dry ingredients into the banana mixture until combined.
For the mocha center, heat heavy cream in a saucepan until warm.
Remove from heat and stir in chocolate chips, espresso powder, cocoa, and vanilla until smooth.
Pour half the banana batter into the loaf pan.
Spread the mocha filling evenly over the batter.
Top with the remaining banana mixture and swirl with a knife.
Bake for 50-55 minutes, until a toothpick inserted in the center comes out mostly clean.
Let cool for 15 minutes, or until you lose patience.