Preheat your oven to 350°F (177°C). Lightly grease an 8 x 8 inch (20 cm) baking pan. Line the bottom and two long sides of the pan with parchment paper to help with easy removal of the bars after baking.

In a mixing bowl, whisk together the all purpose flour, rolled oats, baking soda, and salt until everything is well combined. This ensures that the leavening agents and salt are evenly distributed throughout the mixture.

Cut the unsalted butter into tablespoon-sized pieces and place them in a microwave-safe bowl. Heat the butter in the microwave in 45-second bursts until mostly melted, but with a few solid pieces remaining. Transfer the partially melted butter to the bowl of a stand mixer. Add the packed light brown sugar and white sugar, and cream them together with the butter until smooth and well combined.

Add the smooth peanut butter to the butter-sugar mixture and continue to mix until the mixture is fully smooth and combined. Then, on low speed, beat in the egg and vanilla extract until well incorporated. The dough should be smooth and cohesive at this point. I find using room temperature egg helps the mixture come together more easily.

Gradually stir the dry ingredients from Step 2 into the wet mixture from Step 4, adding about half of the dry mixture at a time. Mix gently until just combined to avoid overmixing. Then, fold in the chocolate chips, reserving a handful to sprinkle on top if desired. Press the peanut butter oat dough evenly into the prepared baking pan and use a flexible spatula to smooth the surface. Sprinkle the reserved chocolate chips over the top.

Bake the bars in the preheated oven for 20 to 25 minutes, or until the edges are light golden brown, slightly puffed up, and just starting to pull away from the sides of the pan. Allow the bars to cool in the pan until they reach room temperature, which takes about 45 to 60 minutes. I like to leave them in the pan so they set completely and are easier to slice.

Once completely cool, use the parchment paper to gently lift the bars out of the pan. Transfer them to a cutting board, slice into bars, and enjoy. For extra flavor, you can sprinkle a pinch of sea salt over the bars before serving—I love the way it complements the chocolate and peanut butter!