Preheat oven to 350°F. Line muffin tins with paper liners or spray with cooking spray. Set aside.
Mix dry ingredients together and set aside.
In a large bowl combine sugar, butter, eggs, and vanilla. Mix well.
Once incorporated, mix in sour cream/or yogurt and milk.
Then slowly add dry mixture to wet, mixing well. Use a whisk if needed to get out any clumps.
Mix in the mashed bananas until well incorporated.
Once mixed, use a large kitchen scoop or spoon to spoon batter into prepared muffin tins. Fill about ¾ full.Sprinkle about 2 tablespoons of crumb topping over each muffin. Bake in preheated oven for 23-25 minutes until tops spring back and/or until a toothpick inserted comes out clean.If your muffins are bigger or have a lot of batter in each cup, they make take up to 28 minutes. Just keep an eye on them and wait until they spring back to the touch. Let muffins rest in tin for 10-15 minutes after you remove them from the oven. The bananas will be very hot and this will give the muffins time to rest.Once slightly cooled, remove from tin and enjoy!