In 4 quart micro proof bowl, mix sugar, milk and butter. Cook on Hi for 20 to 22 minutes, or until a few drops of mixture in cold water forms a soft ball (234 on candy thermometer. Do not leave thermometer in oven while cooking). Stir well every 5 minutes during cooking. Stir in chocolate bits and marshmallow crème. Stir until well blended. Add vanilla and nuts; mix. Pour into buttered 9 inch square dish for thick pieces or 7 1/2 by 12 inch dish for thinner pieces. Cool and cut into squares. Yield: 48 pieces