Preheat your oven to 350°F (180°C) and grease a round baking dish.
In a large mixing bowl, mash three of the bananas until smooth.
Add the softened butter, sugar, eggs, milk, and vanilla extract to the mashed bananas. Mix well.
In a separate bowl, whisk together the flour, baking powder, cinnamon, and salt.
Gradually add the dry ingredients to the banana mixture, stirring until just combined.
Gently fold in the sliced banana, distributing them evenly throughout the batter.
Pour the batter into the prepared baking dish and spread it evenly.
In a small bowl, combine the flour, sugar, melted butter, and cinnamon to create the crumble topping. Mix until crumbly.
Sprinkle the crumble mixture over the batter in the baking dish.
Bake in the preheated oven for about 35-40 minutes, or until the top is golden brown and a toothpick inserted into the center comes out clean.
Once baked, remove from the oven and let it cool for a few minutes.
Serve warm and enjoy!
