Combine sugar, margarine, and milk.

Bring to a rolling boil, stirring constantly.

Boil 5 minutes and remove from heat.
Stir in chocolate pieces until melted.
Add marshmallow cream, nuts and vanilla. Stir quickly until well blended as mixture will begin to cool and harden.
Pour into a greased 9 X 13 inch pan.
Cool and cut into squares.