HEAT oven to 350°F.
COMBINE flour and baking soda. Beat butter and sugars in large bowl with mixer until blended. Add eggs, 1 at a time, mixing on low speed after each just until blended. Gradually beat in flour mixture until blended.
DIVIDE dough in half; place in separate bowls. Add melted chocolate to dough in one bowl; mix well. Add chocolate chips when cooled. Add peanut butter to dough in second bowl; mix well. Stir in peanut butter chips.
Press peanut butter dough in bottom of 9x9 pan and lay chocolate dough on top. Bake until cooked through approx 30 minutes. Let cool completely and add ganache: