With a fork, mix sugar, cinnamon and butter until combined. You want this to be crumbly, you do not want to cream the ingredients. Cover and put in the refrigerator until ready to use.
Muffin Batter
Place bananas into large bowl and mash.
Add sugar, egg and Créme de Banane if using and mix well.
In small bowl sift together flour, baking powder, baking soda and salt.
Add flour to banana mixture in three batches alternately with oil.
Fold in pecans (if using).
Fill prepared tins 3/4 full and top each muffin with streusel.
Bake until tester inserted in center comes out clean, about 20 – 25 minutes. Remove to racks to cool. If making jumbo muffins you will only get 6 and they will take 30 to 35 minutes to bake. Enjoy!