A timeless classic coffee cake filled with a moist and rich dark chocolate flavored with a touch of espresso. A cake you'll come back to time and again.
Position a rack in the center of the oven and preheat to 350 degrees F. Butter and dust with cocoa powder a 10 to 12-cup Bundt pan; set aside.
In a small saucepan, combine the butter, water, cocoa powder, salt, and instant espresso powder. Heat over medium heat until melted, stirring constantly. Set aside and let cool.
In a large bowl, whisk together the flour, sugars, baking soda, baking powder, and orange zest. Add half of the melted butter mixture (the batter will be thick) and stir until completely blended. Then add the remaining melted butter mixture, stirring until completely blended. Stir in the eggs, one at a time, until blended. Fold in the sour cream, vanilla extract, and mashed bananas. Then stir in the chocolate chips.
Spoon the batter into the prepared Bundt pan.
Bake for 40 to 45 minutes, or until a toothpick inserted into the center comes out clean. Let the cake cool in the pan for 15 minutes before inverting the cake onto a rack to cool completely.
Just before serving, dust the cake with powdered sugar.