Streusel Crumb Topping
Place all ingredients for the streusel topping in a small bowl. Use your hands to work the dry ingredients with the butter till they resemble crumb like morsels.
Chill till ready to use.
Preheat the oven to 350 degrees F.
In a medium size bowl, whisk together the all purpose flour, ground oats, baking powder and the baking soda and set aside.
Grease a 12 cup muffin pan or line with paper muffin cups.
In a large bowl, cream together the butter, sugar and the vanilla.
Mix in the egg until combined.
Mix in 1/4 cup of sour cream and half the flour mixture.
Repeat with the remaining sour cream and then the remaining flour.
Fold in the mini chocolate chips and the mashed bananas.
Divide the batter equally among the 12 muffin cups. ( I used an ice cream scoop)
Top each muffin with a heaping tablespoon of the prepared crumb mixture.
Bake for 25 minutes to 30 minutes, or just until a toothpick inserted in the middle comes out clean.
If you are not using the paper liners be sure to let the muffins cool for about10 minutes before releasing them from the pan.