Heat oven to 325F. Grease an 11x15-inch baking pan.
In a microwave-safe dish, melt the baking chocolate with the butter one minute at a time, stirring after each minute, until smooth. Set aside.
Beat together separately the sugar, eggs, vanilla, and salt. Add the butter and chocolate to the sugar mixture. Mix well. Stir in the sifted flour. Spread the brownie batter into the prepared pan. Sprinkle the chocolate chips over top and set aside.
Beat together the peanut butter swirl ingredients. Spoon large dollops of peanut butter mixture all over the top of the chocolate-chip covered brownie batter. Stick a knife into one corner of the pan and, without lifting it, swirl the knife in a zigzag pattern through the batter. Turn the pan and zigzag the knife through the batter again, going against the direction you zigzagged the first time. Do not over blend the peanut butter into the brownie batter.
Bake 25-30 minutes, until still just a tad wet-looking in the center.