Prepare brownie batter according to pkg directions. Spread into greased 13 x 9 pan. Bake at 350 degrees for 20-25 min or until toothpick inserted near the center comes out with moist crumbs.
Sprinkle with peanut butter cups and peanuts. Bake 4-6 minutes longer or until chocolate is melted. Cool on a wire rack.
Meanwhile, in a large saucepan, combine the chocolate chips, peanut butter, butter and salt. Cook and stir until chips are melted and mixture is smooth. Remove from the heat; stir in sereal and vanilla. Carefully spread over brownies. Cover and refrigerate for at least 2 hours before cutting. Yield: 3 dozen.