Whisk bananas, buttermilk, stout beer, eggs, and vegetable oil together in a bowl until just combined. Scrape down the sides of the bowl.

Pour chocolate cake mix into the bowl; stir until thoroughly mixed into the batter. Fold in chocolate chips.

Warm a nonstick skillet or griddle over medium heat. Coat lightly with cooking spray. Drop 1/4 cup batter into the skillet and cook until edges are dry, 2 1/2 to 3 minutes per side. Repeat with remaining batter.