Preheat oven to 350° F. and spray a 9x13 inch pan with non-stick spray.
Place very ripe bananas into a large mixing bowl. Mix the bananas (or mash them) until bananas are pureed or liquified. Add room temperature butter to the bowl, and continue to mix until these two ingredients are combined. Once combined, STIR in the sugar, vanilla extract and eggs, until they are fully blended. Add two cups of flour and a cup of milk to the batter, and continue to stir until they are fully incorporated into the batter. Set aside.
Make crumb streusel topping: Place COLD butter (cut into small chunks), brown sugar and flour in a medium bowl. Cut these ingredients together with a pastry cutter OR by using a fork. Continue until butter becomes the size of peas, and you have a coarse crumb mixture.
Pour HALF of the cake batter into prepared pan. Spread it out, to fill pan. Sprinkle 1/3 of the crumb topping mixture over the batter, to cover. Pour remaining cake batter over the layer of crumb topping (gently spread to cover). Top batter with all the remaining crumb topping, making sure entire surface of cake is covered.
Bake cake in preheated 350° F. oven for 50-55 minutes. Check for doneness at the 50 minute mark. Cake is done when golden brown on top, and very center of cake is set. If you insert a toothpick into center of cake, it should come out clean! Let the cake cool down for 10 minutes (or let it come to room temperature) before you cut into it! Serve, and enjoy!
NOTE: These are large pieces (total of 12 servings). You can also cut the cake into 24 pieces, for a calorie count of 337 per piece.
OPTIONAL: I did not glaze this cake. If you want to add a glaze on top, simply mix 1 cup of powdered sugar with 1-2 Tablespoons of milk, and drizzle on cooled cake.
Banana Crumb Cake https://www.thegratefulgirlcooks.com/banana-crumb-cake/