Preheat the oven to 350 degrees.

Spray a 9X13-inch baking pan with non-stick spray and set aside.

In a large bowl, cream together the butter, peanut butter, brown sugar, and sugar with a mixer until fluffy looking and light in color, 2-3 minutes.

Add in the vanilla, egg and egg yolk. Mix together well.

Add the flour, baking soda, salt and oats into the wet mixture and mix just until combined.

Add chocolate chips and stir to combine together.

Press the batter into the prepared pan.

Bake at 350 degrees 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 20-30 minutes. Serves 12-15.