Grease bottom only of a 13"x9" baking pan; set aside.
Combine brownie mix, syrup pouch, oil, water and eggs; stir until well blended. Mix in one cup chocolate chips; spread in baking pan. Bake at 350 degrees for 30 to 35 minutes or until a toothpick inserted 2 inches from side of pan comes out clean. Immediately sprinkle with marshmallows, remaining one cup chocolate chips and peanuts. Cover pan with a baking sheet for 2 to 3 minutes; remove and cool completely. Cut into 4"x2" bars; store tightly covered.