1. Combine sugar, margarine and milk in a heavy 2-1/2 qt. saucepan. Bring to a boil, stirring constantly. Boil 5 minutes over medium heat or until candy thermometer reaches 238 degrees, stirring constantly.
2. Remove from heat, stir in chocolate pieces until melted.
3. Add marshmallow cream, nuts, vanilla; beat until well blended. Pour into 9x13 pan. Cool and cut into squares. Makes 3 lbs.
* Mint Fantasty: Add 1 cup party minuts or butter mints; omit nuts.
* Peanut Brittle Fantasy: Add 1 cup peanut brittle, crushed; omit nuts.