The day before you plan to make this recipe, leave the milk chocolate in a warm place to make it slightly pliable. Cut each bar into 8 chunks and, with your hands, try to form each chunk into a disk the size of a quarter with no sharp edges. Lay the wonton skins out on a surface and 1 at a time; paint the edges with water. In the center of the wonton skin, place a disk of milk chocolate and a banana slice on top of the chocolate. Fold the wonton skin corner to corner to make a triangle and press together well to seal completely. Cover with plastic wrap and store chilled until ready to fry and serve, up to 10 hours ahead.
Heat the oil in a deep pot to 350 degrees. Drop the wontons into the oil, being careful not to crowd them (you may have to work in batches) and fry, turning often, until golden brown. Meanwhile, place the cinnamon sugar in a bowl. Remove the wontons with a slotted spoon and immediately dredge them in the cinnamon sugar to coat heavily. Serve right away with scoops of vanilla ice cream.