1/2 c. butter, softened 3/4 c. peanut butter 2 1/2 tsp. vanilla extract 1 1/2 c. dark brown sugar 2 1/2 c. powdered sugar 1 c. chocolate chips + 1 more cup for topping if desired

In a large bowl, whisk together butter, peanut butter, vanilla, and brown sugar. Add powdered sugar and mix until combined. Fold in chocolate chips and press into a greased pan (mine was small - like 5x6, but you could use a bigger pan for thinner bars) If desired, melt 1 c. chocolate chips and pour on top. Chill in refrigerator for 2+ hours and cut into squares.