Add all ingredients except the chocolate chips to the prepared baking dish - bananas, oats, maple syrup, baking powder, cinnamon, salt, milk, egg, melted butter, and vanilla extract. Stir together until well combined. Top with dark chocolate chips.
2 cups old-fashioned rolled oats, 1/3 cup maple syrup, 1/4 cup cocoa powder, 1 teaspoon baking powder, 1 teaspoon cinnamon, 1/2 teaspoon salt, 2 cups milk of choice, 3 whole bananas, mashed, 1 large egg, 1 teaspoon vanilla, 2 Tablespoons unsalted butter, melted, 1/2 cup dark chocolate chips