Line a 13-in. x 9-in. baking pan with foil and grease the foil with 1-1/2 teaspoons butter; set aside.
In a large saucepan, combine the chocolate chips, milk and remaining butter. Cook and stir over medium heat until mixture is smooth. Remove from the heat; stir in peanuts. Place marshmallows in a large bowl; add chocolate mixture and stir well. Spread into prepared pan. Refrigerate until firm.
Using foil, lift fudge out of pan. Cut into 1-1/2-in. squares. Yield: about 2-1/2 pounds.