For the banana bread:
1. Mix all wet ingredients, including the bananas in a medium sized bowl.
2. Mix the dry ingredients in a separate bowl.
3. Add the dry ingredients to the banana mixture and stir just until combined.
4. Pour the batter into a greased 9x5 bread pan and let it rest for 10 minutes.
For the Crumble topping:
1. Combine the crumble topping ingredients with your fingers until it is coarse and crumbly.
2. Sprinkle it on top of the banana bread mixture, then bake at 350 for 50-65 minutes, or 20-25 minutes for muffins.
3. It is done when a toothpick or knife inserted in the center comes out clean, or with a few moist crumbs. This makes a 9x5 bread pan or 15 muffins.
Note: If you would like to lower the sugar, lowering it to 1/2 c sugar results in a mildly sweet tender muffin. The effect of the lower sugar amount is especially small if you make the crumble topping.