Step 1

Preheat oven to 350º F. Grease a 9" x 13" baking dish with butter or cooking spray; set aside.

Step 2

In a large bowl, use your hands or two forks to crumble together the cold butter cubes, flour, sugars, and cinnamon until the mixture resembles a crumbly topping. Set aside the crumb mixture.

Step 3

In a large bowl, whisk together flour, baking powder, cinnamon, and salt. Set aside.

Step 4

In a stand mixer, mix softened butter on medium until creamy, about 2 minutes. Add the sugar and mix for another minute, until well incorporated. Then add the eggs, vanilla, and mashed bananas, and mix just until ingredients are incorporated (do not overmix!)

Step 5

Turn the mixer down to low, and alternate mixing in milk and flour until all ingredients are combined.

Step 6

Pour half of the cake mixture into the prepared baking dish. Top with 1/3 - 1/4 of the crumb mixture. Then pour the remaining cake mixture on top of that layer and finally, top evenly with the remaining crumb topping.

Step 7

Bake at 350º for 50-55 minutes, until a toothpick comes out clean.

Step 8

To make the optional glaze: In a small bowl, whisk together the powdered sugar and 1 tablespoon of milk. Add more milk as needed until you get the glaze consistency you prefer. Set aside.

Step 9

Cool at room temperature for 5-10 minutes before drizzling the glaze over the top, slicing, and serving.