Lightly grease a large bowl and place the popcorn in it.
In a large saucepan, combine the sugar, corn syrup, and water and cook over medium heat to the soft ball stage, 235 to 238 degrees F on a candy thermometer. Add the butter and when melted, stir in the chocolate and vanilla.
Very carefully, slowly pour the hot chocolate mixture over the corn, stirring to prevent from lumping. Continue stirring until the mixture is cooled and the popcorn is evenly coated. Add the remaining ingredients and stir to combine and coat. Turn out onto a silpat or a greased foil-lined sheet pan. Let cool, then store in airtight containers.
Yield: about 14 cups