Preheat the oven to 350 degrees and grease a 9x13 baking pan with butter.
Whisk together flour, baking soda, salt, and oats.
In your mixer, blend together butter, peanut butter, brown sugar, and sugar for about 2-3 minutes until it's smooth.
Add vanilla, egg, and egg yolk and mix well.
Add dry ingredients.
Add candy bars and combine well.
Press the batter into your baking pan. Take some leftover candy pieces and press them on top for extra "presentation points!"
Bake for 15-16 minutes, until edges are lightly browned.
Let cool for 30-45 minutes. Cut into squares and enjoy!