Preheat oven to 350˚F.

In the bowl of an electric mixer, combine the sugar and butter beating at medium speed until fluffy. On low-speed, add the banana, milk, greek yogurt and eggs mixing until combined.

In a small bowl, whisk together the flour, baking soda and salt. Keeping the mixer on low-speed and slowly add the dry ingredients to the wet ingredients. Beat just until blended.

Divide the batter evenly between the wells of a muffin tin lined with cupcake papers or coated with cooking spray filling halfway.

Using a fork, stir together the butter, flour and brown sugar in a small bowl until pea sized crumbs form. Sprinkle the crumb topping evenly over the top of the muffin batter.

Bake at 350˚F for 20 minutes or until a toothpick inserted into the center comes out clean. Cool in pan for 10 minutes on a wire rack. Remove from pan and cool on rack.