1. Mix together butter, brown sugar, sugar, egg, vanilla extract and mashed bananas until well combined.
2. Add flour, cinnamon, baking soda, cloves and cornstarch and mix until combined.
3. Stir in oats.
4. Preheat oven to 350 degrees.
5. Spoon tablespoons of dough onto a cookie sheet covered with parchment paper. Flatten dough a little bit, into thick discs. They will spread a little when baked.
6. Bake for 10-12 minutes or until edges just start to golden.
7. Remove from oven and cool on cookie sheet for 3-4 minutes, then move to cooling rack to finish cooling.