Line an 8x8 inch square brownie pan with parchment paper. Place 1 1/2 cups semi-sweet chocolate chips and 2 tablespoon peanut butter in a small sauce pan. Heat over low heat, stirring often until melted and smooth. Alternately, you can do this in the microwave on 30 second intervals, stirring after each interval until melted and smooth. Pour the chocolate mixture into the prepared pan and tap against the counter until the chocolate is in a smooth and even layer. Cover and place in the fridge for 30 minutes to harden. Meanwhile, add the stick of softened butter, 1 1/2 cups creamy peanut butter, 2 tsps. vanilla and 1 cup powdered sugar to a large mixing bowl or the bowl of a stand mixer. Beat until smooth and creamy. Taste and add more powdered sugar to your liking. Spoon the peanut butter mixture over the chocolate layer into a smooth layer. Place back in the fridge. Place the remaining 1 1/2 cups semi-sweet chocolate chips and remaining 2 tablespoons peanut butter in a small sauce pan. Heat over low heat, stirring often until melted and smooth. Again, alternately, you can do this in the microwave on 30 second intervals, stirring after each interval until melted and smooth. Pour the chocolate mixture over the peanut butter layer, smooth the chocolate out into an even layer. Cover and place in the fridge for 1-2 hours or until ready to serve. Slice into bars and keep refrigerated.