Line your 8x8 baking pan with wax paper on all four sides (this helps the peanut butter not stick!). Melt the peanut butter in the microwave or on the stove. Pour the melted peanut butter into the pan and then freeze for one to two hours - you’ll know it’s ready when you can remove the peanut butter in one piece.
Once the peanut butter has frozen, preheat the oven to 350°F. Take the frozen baking pan out of the freezer and remove the wax paper with the peanut butter. Line the pan with parchment paper, making sure it is slightly overhanging so you can easily lift the blondies out once cooled.
Melt the butter in a large bowl in the microwave or in a small pan over the stove.
Add in both the sugars and use a whisk to whisk the butter and sugars together. Keep whisking until the mixture resembles a paste that pulls away cleanly from the side of the bowl when you mix it. Add the eggs and vanilla and mix again.
Pour the flour and salt into the bowl and mix with the whisk until just combined (it should only take about a minute). This is important, because over-mixing at this stage will affect the texture of the blondies!
Gently fold in the chocolate chips until just combined.
Pour half of the blondie batter into the prepared pan. Peel the peanut butter layer off of the wax paper and place it on top of the blondie batter.
Pour the rest of the blondie batter on top and spread it so it is evenly covering the peanut butter layer. You can sprinkle more chocolate chips or peanut butter chips on top now if you wish!
Bake for 25-35 minutes. The top of the blondies should be crinkly and when you insert a toothpick in the middle the toothpick should not come out clean. The blondies are ready when the toothpick has a few wet crumbs, but not wet batter.
Let the blondies cool completely before slicing. Enjoy!