1. For thicker bars use a 9x9 inch pan and bake 28 to 35 minutes 2. do not overbake for chewy texture and remove when center is just set 3. swap chocolate chips for butterscotch chips or white chocolate chips 4. add 1 tbsp espresso powder to boost chocolate flavor 5. store airtight at room temperature up to 4 days or freeze up to 2 months