Preheat oven to 350F. Line a 9″ x 13″ baking pan with parchment paper. I cut it so that it’s 9″ wide and long enough to hang over the other two ends because this makes it easy to pull out of the pan after they are cooked.
In the bowl of a standing mixer, beat butter and brown sugar until creamy. Add eggs and vanilla, mixing until combined. Scrape down the sides and bottom of the bowl with a rubber spatula as needed.
In a separate large bowl, whisk together the flour, baking powder and salt. Gradually add to butter mixture and mix on low or medium-low until combined. Use a wooden spoon to stir the chocolate chips in by hand. Evenly spread into prepared pan.
Bake for about 30 minutes until edges are golden brown and the middle is set. Do not overbake. Let cool, then cut into bars.