Line an 8x8 baking dish with parchment paper.
Preheat the oven to 350 degrees.
Begin by making your peanut butter filling.
Combine all the peanut butter, melted butter, brown sugar and vanilla in a small bowl. Stir by hand for 1 minute, or until the mixture is smooth.
Add powdered sugar and mix until the mixture is soft and pliable.
Set aside.
Combine melted butter, brown sugar and granulated sugar in a mixing bowl.
Stir until well combined.
Add egg and vanilla and mix well.
Add cocoa, flour and baking soda, mix until all of the ingredients are incorporated.
Divide the dough in half.
Press half of the cookie dough in the bottom of your prepared baking dish.
Sprinkle half of the chocolate chips over the cookie dough.
Divide the peanut butter filling in half.
Spread half of it over the cookie dough.
Add the remaining cookie dough to the top and spread it to cover the peanut butter layer.
With the remaining peanut butter filling, you can form little peanut butter balls by hand, there should be just enough to make ten balls.
Place nine of these over the top.
The remaining peanut butter ball is intended to be popped into your mouth and taste tested.
Bake at 350 for 23 minutes.
Remove from the oven and sprinkle the remaining chocolate chips over the top.
Allow to cool completely before cutting.
Once the cookie bars are cooled, you can gently lift the parchment paper from the dish and cut into 9 delicious servings.