Preheat oven to 350 degrees F. Line a sheet pan with parchment paper.

In the bowl of a stand mixer fitted with a paddle attachment, beat together the butter, peanut butter, and brown sugar on medium high speed until pale in color and creamy, 4-5 minutes (don't skimp on time!). Scrape down the bowl as necessary. Mix in the vanilla extract and egg.

In a separate bowl combine the flour, baking soda, and salt. Add to the stand mixer and mix on medium low speed until combined. Add the chocolate chips and mix on low until just combined. The mixture may be a little crumbly, but should form into rounds when pressed together with your hands.

Scoop into 1/4 cup rounds (1 1/2 tablespoon rounds for regular sized cookies) and place on prepared sheet pan. Bake until cookies just begin to turn brown, 12-15 minutes (8-10 minutes for regular sized cookies). Do not over bake.

Let cookies cool on the pan for 5 minutes, then place on a wire rack to cool completely. Store cookies in an airtight container at room temperature for up to 1 week.