Combine sugar, margarine and milk in heavy 2-1/2 quart saucepan; bring to full rolling bail, stirring constantly. Continue boiling 5 minutes over medium heat, stirring. Remove from heat, stir in chocolate till melted. Add marshmallow creme, nuts & vanilla beat till blended. Pour into greased 13 x 9-inch baking pan. Let cool and cut into 1-inch squares.
Microwave margarine in 4-quart microwave-safe bowl on HIGH (100%) 1 minute or until melted. Add sugar and milk; mix well. Microwave on HIGH 5 minutes or until mixture begins to boil, stirring after 3 minutes. Mix well; scrape bowl. Continue microwaving on HIGH 5-1/2 minutes; stir after 3 minutes. Stir in chips until melted. Add remaining ingredients; mix well. Pour into greased 13 x 9-inch baking pan. Cool at room temperature; cut into squares. Makes 3 pounds.
Note: Can be made in a smaller pan for thicker squares
Peanut Butter Variation: drop a few spoonfuls of peanut butter on top of fudge and swirl around. Let cool.