Add the croissant pieces, making sure all the croissant pieces are soaked. Make sure they absorb the liquid. Sprinkle the chocolate chunks over the croissant mixture, tossing gently. Add the bananas, if you desire, and toss. Place the ramekins on a sheet pan and place it in the oven, or if you are using the 8 x 8 pan place directly on the rack in the oven. Bake for about 30-35 minutes, or until the bread pudding is set and golden brown on top. Remove the bread pudding from the oven and let it cool slightly. Dust with powdered sugar, if desired.