In a large bowl mix together the flours, sugar, baking powder and salt. Add the egg, milk, vanilla and butter; stir until thoroughly combined (batter may be slightly lumpy).Place a buttered griddle over medium heat.Place 6-8 banana rounds on the griddle, about 3 inches apart. Spoon a scant tablespoon batter over each banana slice; cook until large bubbles cover surface, 1 to 2 minutes. Flip, and cook until bottom is golden, about 1 minute more.Serve immediately.