In 9x13 pan, either line with foil or spray with non-stick spray. In bowl put chocolate chips, chocolate bar, marshmallow creme, mini marshmallows and vanilla. I use the kitchen aid bowl. In heavy 3 quart sauce pan, bring sugar, milk and butter to a full rolling boil over medium heat. Stir carefully so not to splash up the sides of the pan. Keep the build up off the side of the pan using a rubber spatula. Boil until 232 on a candy thermometer. Remove from heat, carefully pour over chocolates/marshmallows. Using the paddle on Kitchen aid, carefully put the paddle on, lower the paddle into the mixture and very carefully pulse the machine at first, then continue on lowest level for several minutes, watching to assure that all marshmallows are melted. Scrape down sides, and continue to mix thoroughly. Add nuts if desired, mix. Pour onto prepared pan and spread evenly. Allow to set at least 1-2 hours, cut as desired.