1Heat oven to 350°F. In large bowl, stir double chocolate chunk cookie mix, 1/4 cup oil, 2 tablespoons milk and 1 egg until soft dough forms. Drop dough by tablespoonfuls evenly over bottom of ungreased 13x9-inch pan.
2In same large bowl, stir peanut butter cookie mix, 3 tablespoons oil, 1 tablespoon milk and 1 egg until soft dough forms. Drop dough by tablespoonfuls over chocolate dough in pan. Swirl doughs together slightly, using metal spatula; spread and press evenly in pan.
3Bake 25 to 27 minutes or until edges are light golden brown. Remove from oven; sprinkle evenly with chocolate chips. Let stand 2 minutes.
4In small bowl, stir powdered sugar, peanut butter and enough of the 2 to 3 tablespoons milk until frosting is smooth and spreadable. Spoon frosting over chocolate chips; lightly swirl chocolate and frosting together. Sprinkle with peanuts; press lightly into topping. Cool completely, about 30 minutes. For bars, cut into 9 rows by 4 rows.