In a large bowl add your bananas and mash thoroughly then add the eggs and whisk to combine.
Add the brown sugar, white sugar, oil, buttermilk and rum and whisk until smooth and homogenous.
Add the remaining dry ingredients (flour, baking powder, baking soda, salt and cinnamon) and mix until just combined.
Fill your muffin cups to the halfway point and top with a tablespoon of the sticky dates. Top with the remaining batter and dates before using a cake tester or skewer to swirl the dates and muffin mix together.
Sprinkle the crumble mixture evenly over the tops of the muffins.
Transfer to the oven and bake at 425F for 5 minutes then lower the temperature to 350F for an additional 20-25 minutes until the muffins are 200F internally or a cake tester has only a few crumbs on it. Enjoy!