Preheat the oven to 175°C (350°F) and grease or line a 9x5-inch loaf pan with parchment paper.

In a mixing bowl whisk together mashed bananas, granulated sugar, brown sugar, vegetable oil, eggs, and vanilla extract until smooth.

In a separate bowl combine flour, baking powder, baking soda, salt, and ground cinnamon and whisk to evenly distribute.

Add the dry ingredients to the banana mixture alternately with the milk, stirring gently with a spatula just until no dry flour remains.

In another bowl mix melted butter, brown sugar, ground cinnamon, flour, and chopped nuts (if using) with a fork until a crumbly mixture forms.

Pour half of the banana bread batter into the prepared loaf pan and spread it into an even layer.

Sprinkle about one-third of the cinnamon crunch mixture evenly over the batter layer.

Add the remaining batter on top, spreading gently to cover the cinnamon layer without overmixing.

Sprinkle the remaining cinnamon crunch mixture evenly over the top of the loaf, lightly pressing it into the batter.

Bake the banana bread for 50 to 60 minutes, or until a toothpick inserted into the center comes out mostly clean with a few moist crumbs.

Remove the pan from the oven and let the banana bread cool in the pan on a cooling rack for 15 minutes.

Carefully loosen the edges with a butter knife, lift or invert the loaf from the pan, and let it cool completely on the rack for at least 5 more minutes before slicing.