Preheat oven to 350°. Lightly butter an 8-inch square baking dish or 6 (8-ounce) ramekins.
Stir together first 5 ingredients in a medium bowl. Stir in butter and bitters.
Place half of banana slices in bottom of baking dish or evenly in bottoms of ramekins. Sprinkle with half of breadcrumb mixture. Repeat with remaining bananas and remaining breadcrumb mixture. Bake 35 minutes. Serve with Bitters-and-Butter Sauce.