Preheat oven to 350 degrees. Spray a 9 x 5-inch loaf pan with nonstick cooking spray; set aside.
Mix butter and sugar until light and fluffy, using a stand mixer (or hand mixer).
Add eggs and vanilla; mix until fully incorporated.
Stir in bananas by hand.
In a separate bowl, whisk together flour, cocoa powder, salt, baking soda, and baking powder.
Using a spatula, gently fold flour into butter mixture. Do not overmix; there should still be a little flour visible when you are done.
Add chocolate chunks / chips to batter, then gently fold in with spatula.
Transfer batter to loaf pan; top with a few extra chocolate chunks / chips, if desired. Bake for about 45 to 50 minutes, or until a toothpick inserted in the center comes out mostly clean.
Cool bread before slicing. Enjoy!
Notes
Check out info before this recipe cards for lots of tips and tricks, plus some tasty variations!I used natural cocoa powder and a chopped up a Lindt candy bar for the chocolate chunks in this recipe. Dark or bittersweet chocolate will give you the richest flavor, however you may uses other types of chunks / chips as well, such as milk chocolate or even white chocolate.