1) In the bowl of a food processor, combine the sugar and vanilla and pulse for 5 to 6 seconds until well combined.
2) Coarsely chop the semi-sweet and milk chocolates and add them to the bowl. Pulse in 10 second intervals until until finely ground and combined with the vanilla sugar.
3) Add the dry cocoa and salt, pulsing again until everything is well mixed. The mix will be slightly coarse, like brown sugar. Pour into a large glass or plastic jar for storing.
4) For each cup of hot chocolate, combine 1/4 cup of mix with 8 ounces of hot milk. Stir until all of the chocolate is melted. Top with whipped cream, marshmallows or your favorite topping. Makes 24 8-ounce servings.
Store airtight for 6 to 9 months. Excellent for holiday gift giving. Try packing in pretty mason jars tied with bright ribbons. Be sure to add a card with the mix directions.