1. Mix the flour, baking soda, baking powder, and salt. 2. Mix bananas, sugar, egg and butter and combine with dry mixture just until moistened. 3. Fill muffin cups 3/4 full. 4. For the topping combine the brown sugar, flour, and cinnamon. 5. Cut in butter until crumbly and sprinkle over muffins. 6. Bake at 375° for about 20 minutes, until muffins test done. 7. Cool in pan for 10 minutes.