Step 1: Preheat your oven to 350°F (175°C) and line an 8×8 inch baking pan with parchment paper, leaving a slight overhang on the sides for easy removal.
Step 2: In a large mixing bowl, cream together the softened butter, creamy peanut butter, and brown sugar until the mixture is light and fluffy.
Step 3: Add the egg and vanilla extract to the bowl and beat until fully incorporated and smooth.
Step 4: Sift in the flour, baking soda, and salt. Use a spatula to gently fold the dry ingredients into the wet mixture until just combined.
Step 5: Fold in 1 cup of the chocolate chips, ensuring they are evenly distributed throughout the thick dough.
Step 6: Press the dough evenly into the prepared baking pan. Sprinkle the remaining 1/2 cup of chocolate chips over the top, pressing them in slightly.
Step 7: Bake for 22-25 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out with just a few moist crumbs.
Step 8: Remove from the oven and sprinkle with sea salt if desired. Allow the bars to cool completely in the pan before slicing into 16 squares.