1.Preheat oven to 350 degrees. Mist an 8 x 8 or 9 x 9 baking pan with cooking spray then line with parchment paper with a slight overhang for easy removal and mist lightly again. Set aside.
2.In a medium to large mixing bowl, add the butter along with the peanut butter and mix with an electric mixer until nicely combined and creamy.
3.Add the brown sugar and vanilla, mix again until completely combined.
4.Now add the flours, baking powder and salt until well combined.
5.Take a rubber spatula and make sure all the dry ingredients that may be on the bottom of the bowl is incorporated well into the batter.
6.Spread the batter into the prepared pan. I used a 9 x 9 pan. Use clean hands for best results to spread the mixture to the corners of the pan.
7.Bake for about 25 minutes until slightly puffed up. Make sure you turn the pan around after about 15 minutes for even baking. At this time tap the pan a few times on the rack.
8.Take out of the oven and cool on wire rack until completely cooled. Pull the parchment paper up to remove from the pan. In the meantime, melt your chocolate chips in the microwave for 30 seconds, take out stir and place back in for another 20 seconds, stir again do this until chocolate is melted and smooth.
9.Now drizzle or spread over the square and let cool and set up. Do not put in fridge
10.When set up, cut into 12 squares. Store for up to 4 days in an airtight container. Enjoy!