Preheat oven to 350 degrees.
Prepare brownie batter according to package directions. Spread into a greased 13x9-inch baking pan; bake for 20-25 minutes or until a 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.
After the brownies have cooled, combine the chocolate chips, peanut butter, butter and salt in a medium saucepan. Cook and stir until chips are melted and mixture is smooth. Remove from the heat; stir in cereal and vanilla. Carefully spread over brownies. Cover and refrigerate for at least 2 hours before cutting. Yield: 3 dozen.