Preheat your oven to 350°F (176°C). Grease an 8x8-inch baking pan with butter or non-stick spray. Line it with parchment paper, leaving an overhang on two sides for easy lifting later.

Grab a medium bowl and whisk together the flour, baking soda, and cornstarch. Set this mixture aside for later. This step ensures your bars rise evenly and stay tender.

Melt the unsalted butter and allow it to cool slightly. Mix it with light and dark brown sugar in a large bowl. Whisk until the mixture becomes smooth and free of lumps.

Whisk in the eggs and vanilla extract until fully incorporated. Follow this with the creamy peanut butter, which gives the bars their rich and nutty flavor.

Slowly fold the dry ingredients into the wet mixture using a spatula. Be gentle to avoid over-mixing, which can make the bars dense.

Pour in the semi-sweet chocolate chips and mix until they’re evenly distributed. You can add extras on top for a pretty finish if you like!

Spread the dough evenly into the prepared pan. Pop it into the oven for 28-35 minutes. You’ll know it’s ready when a toothpick inserted in the center comes out with a few moist crumbs.

Allow the bars to cool in the pan for 10–15 minutes. Lift them out carefully using the parchment paper and slice into squares. Serve and enjoy!