- Preheat the oven to 350 degrees. Lightly grease a 9X13-inch baking pan and set aside.
- In a medium bowl, whisk together the flour, baking soda, salt and oats.
- In a large bowl, or in the bowl of a stand mixer fitted with the paddle attachment, cream together the butter, peanut butter, brown sugar, and sugar until fluffy looking and light in color, 2-3 minutes.
- Add in the vanilla, egg and egg yolk. Mix together well.
- Add the dry ingredients into the wet and mix just until combined.
- Add the chopped candy bars and combine together.
- Press the batter into the prepared pan. Press a few additional chopped candy on top of the dough for a pretty presentation.
- Bake for 15-18 minutes or until lightly browned on the edges. The bars will still look pale and slightly underdone in the middle. That's ok. Don't over bake or the bars will be dry!
- Let the bars cool in the baking pan for 30 minutes. Cut into squares and enjoy!