Grease square pan with butter.

2 (12 oz.) pkgs. chocolate chips
2 c. chopped nuts
4 c. granulated sugar
1 lg. can Pet milk
2 tsp. vanilla
2 c. marshmallow whip
1/2 lb. butter, cut into small pieces

Combine milk and sugar in small pan and boil 4 minutes. In large bowl combine chocolate chips and marshmallow whip. Blend together. Pour hot mixture over chocolate chips, marshmallow whip, chopped nuts, and cut up pieces of butter and mix and blend well. Pour into buttered pan. Cool and cut into pieces.