Peanut Butter M&M Cookie Bars

1. Preheat oven to 350ºF. Lightly spray a 8×8 baking dish with nonstick cooking spray.
2. In the bowl of a stand mixer, cream together butter and sugars. Add in peanut butter, egg, and vanilla extract and beat until smooth.
3. In a small bowl, whisk together flour, baking soda, and salt. Add dry ingredients to wet ingredients and beat until well-combined. Stir in peanut butter M&Ms.
4. Spread batter into prepared baking dish. Bake for 13-15 minutes or until edges just start to turn golden brown. Do not over-bake.
5. Cut into pieces and store leftovers in an airtight container.