In a mixing bowl add the butter and sugar. Mix on medium speed until creamy. Add the eggs and the banana, mix well. Turn the mixe on low spead, add the flour, soda and baking powder. Continue mixing until all the ingredients are well blended. Add in the sour cream and mix. Stir in the chocolate chips.Using an ice cream scoop, scoop a heaping spoonful into each muffin cup. In a small bowl add the strusel ingredients. Butter, brown sugar and the flour. Mix with a fork until combined and crumbly.Sprinkle the strusel on the top of each muffin.Bake in a 350 degree oven for 20 min. Remove and cool. Enjoy