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

In a large bowl, crumble together the cold butter cubes, flour, sugars, and cinnamon until the mixture resembles a crumbly topping. Set aside the crumb mixture.

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

In a stand mixer, mix softened butter on medium until creamy, about 2 minutes. Add the sugar and mix for another minute. Then add the eggs, vanilla, and mashed bananas, and mix just until incorporated.

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

Pour half of the cake mixture into the prepared baking dish. Top with 1/3 – 1/4 of the crumb mixture. Pour the remaining cake mixture on top and then top evenly with the remaining crumb topping.

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

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.

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