Preheat oven to 375 degrees. Line a 12 cup muffin pan with paper liners.Combine flour, cinnamon, baking soda, baking powder, and salt in a large bowl. Toss blueberries in to coat in dry ingredient mixture.In a separate bowl, mix together mashed bananas, carrot, sugar, egg, yogurt, vanilla and melted butter or if you are using a lighter recipe, the oil + applesauce.Add in flour mixture and stir just until combined. (Do not overmix)Divide batter evenly into 12 muffin cups using a full sized ice cream scoop. Batter will be almost to the top of the muffin liners.In a small bowl combine brown sugar, cinnamon, flour and cold butter until mixed. Using your fingers incorporate the oatmeal and nuts. You want a crumbly mixture.Divide topping over muffins.Bake 20 -25 minutes or until a toothpick comes out clean.