1. Make the streusel by combining all the ingredients and mashing the butter in until crumbly. Set aside.2. Mix the flour, salt, and baking powder together. Set aside.3. Mix the butter and the sugars together.4. Stir in the egg, egg yolk, and the vanilla.5. Mash the ripe bananas and add them in. 6. Blend together smoothly.7. Preheat the oven to 375 degrees. 8. Now, add the dry ingredients to the wet ingredients. Stir until evenly combined. Be careful not to over-stir. The batter can get overworked causing the muffins to not be as moist. 9. Beat the egg white to a soft peak (You can do this ahead of time and set it aside to have it ready for this step). Fold it in the batter along with the chopped pecans.10. Put the banana nut muffin batter into the cupcake liner up to about 3/4 way up. 11. Sprinkle the streusel on top of the batter evenly among each muffin. 12. Bake for 20-22 minutes or until fully baked. 13. Enjoy!
Notes
You can exclude the pecans from the batter if you choose.