Combine sugar, margarine, and milk in heavy 2.5qt saucepan; bring to full rolling bowl, stirring constantly. Continue boiling 5 min over medium heat or until candy thermometer reaches 110ºC stirring constantly to prevent scorching. Remove from heat; stir in chips until melted. Add marshmallow creme, nuts and vanilla; beat until well blended. Pour into greased 9x13 inch pan. Cool at room temperature, cut into squares. Makes approx 3lb.