In a large bowl, whisk together flour, sugar, baking powder, cornstarch, and salt.
Place 1 banana, egg, milk, melted butter, and vanilla in a blender and blend on medium speed until well-combined
Pour the liquid mixture into the bowl with dry ingredients and stir until just combined, taking care not to over-mix. Fold in 3 Tbsp rainbow sprinkles.
Lightly spray each side of the Waffle Puff Pan with cooking oil. Pre-heat pan on medium heat for 3 minutes. Add ¾ cup of banana waffle batter filling in all the bubbles. Flip the waffle maker over and cook for 3 minutes. Flip the waffle maker again and cook for another 3 minutes or until golden brown.
Remove waffle with fork and gently fold into taco shell shape. Rest waffle in a spot where it will hold its shape (like a loaf pan) and let cool for at least 10 minutes. Continue with remaining batter for second waffle.
Slice remaining banana. Fill each bubble waffle with 3 scoops of ice cream and divide sliced bananas, sliced strawberries, and chopped walnuts among the two shells. Top each bubble waffle shell with chocolate syrup and whipped cream. Sprinkle remaining sprinkles over the top and add on a maraschino cherry.