Preheat oven to 350 degrees F.
1. Combine flour, salt, baking soda and cinnamon in a bowl and set aside.
2. In a large bowl, mix brown sugar and butter. Add mashed banana, egga and vanilla.
3. Add flour mixture to butter mixture and mix well.
4. Stir in rolled oats.
5. Add walnuts (optional).
6. Drop cookies by teaspoonfuls onto a non-stick cookie sheets. Leave about 2 inches between cookies for spreading.
7. Bake for 8 to 10 minutes or until golden brown. Cool for 5 minutes before transferring to wire racks to cool completely.