Preheat oven to 350 degrees F. Line a 9x13-inch baking pan with parchment paper, allowing excess paper to hang over pan edges.
Combine flour, baking powder, and salt in a small bowl and set aside.
With your mixer, beat the butter and brown sugar together until smooth. Add the eggs and vanilla and beat until well incorporated. Then add in the peanut butter until combined.
Now add the flour mixture and stir until just incorporated, and add the peanut butter chips just until evenly mixed.
Spoon the batter into the prepared pan and smooth the top. Bake 30 to 35 minutes. Cool completely.
Remove the lid and foil and microwave chocolate frosting for 30-60 seconds until pourable consistency. Pour over the blondies, smoothing evenly.
Top with chopped peanuts or chocolate chips. Refridgerate atleast 2 hours before cutting.
Using the paper overhang, lift the blondies from the pan and transfer to a cutting board. Cut into small squares. Store in an airtight container in the fridge.