Cookie Base: 

• Preheat oven to 350° and spray 8x8 inch pan with non-stick spray, and line with parchment paper. 
• In a medium bowl, whisk together dry ingredients; flour, rolled oats, baking soda, cinnamon, and salt. 
• In a large bowl or bowl of a stand mixer, cream together butter and sugars on medium speed for 2-3 minutes or until the mixture looks light, fluffy, and pale in color. Add the egg and vanilla extract and continue to mix on medium speed for another 1-2 minutes until the mixture is well combined and fluffy. 
• Add in the flour mixture, mixing on low until combined. Scrape down the sides of the bowl to ensure all the flour is incorporated. 
• Press dough evenly into the bottom of the prepared 8x8-inch pan. Bake for 15 minutes or until the edges of the dough turn lightly golden brown. 

Banana Blueberry Filling 

• In a medium bowl, mash the bananas 
• Stir in brown sugar, cinnamon, and vanilla
• Fold in blueberries 

Oat Crumble: 

• In another bowl, combine flour, oats, brown sugar, and cinnamon. 
• Add cold cubed butter (~1 in./2.5cm) into dry ingredients. Using your fingers or pastry cutter, combine the butter with the flour mixture until the mixture resembles a coarse crumb. Set aside.

Assemble: 

• Once the cookie base is done, spread the banana blueberry filling evenly. Then add the crumble over the top.
• Bake at 350° for 20 minutes; the top is lightly golden brown. Allow bars to cool completely at room temperature.