Preheat oven to 450°.
Place a 9-inch cast-iron skillet in a 450° oven for 15 minutes. Combine first 5 ingredients, stirring with a whisk until smooth. Melt 1 tablespoon butter in preheated pan until browned, swirling to evenly coat pan. Add batter; sprinkle evenly with chocolate chips. Bake at 450° for 10 minutes or until puffed and browned.
Cut banana halves in half crosswise. Melt 1 tablespoon butter in a large skillet over medium-high heat. Add bananas; cook 2 minutes on each side or until browned. Add liqueur; simmer 1 minute. Serve with Dutch baby; top with whipped topping.