Simply fill the bananas with pieces of a broken chocolate bar. My favourite is 70% dark chocolate. I prefer buying the Lindt brand because their chocolate block is thinner, which makes stuffing bananas easier, but any good quality chocolate will do. If you are going to peel the bananas and bake them in a skillet, you can experiment with all sorts of ingredients. Honey, cinnamon, maple syrup, rum, brown sugar, peanut butter, nuts (walnuts or hazelnuts) or even marshmallows are all excellent choices.