To prepare hot chocolate mix at home, combine 2 cups powdered sugar, 1 cup Dutch-process cocoa, 2 1/2 cups powdered milk, 2 teaspoons cornstarch and 1 teaspoon salt, and store the mixture in an airtight container. You can also add a pinch of cayenne pepper.
To prepare a mug of hot chocolate from the mix, fill the mug half full with the cocoa mixture, and pour in hot water. Stir to combine, and serve immediately. You can also use warm milk for a creamier beverage. Keep the rest of the hot chocolate mix stored in the pantry indefinitely. For a Mexican-style variation, add some cinnamon to the mix along with the cayenne pepper. Add a splash of peppermint schnapps for adult guests, or combine the beverage with coffee for a creamy mocha. Also consider using a granulated sweetener such as Splenda to replace the sugar, or substitute instant coffee creamer for some of the powdered milk to make a creamier version.
Adding a pinch of cayenne brings out the chocolate flavor, and adding a little more gives the hot chocolate a spicy touch. For a special treat, place a dollop of whipped cream over a mug of prepared hot chocolate, and sprinkle cinnamon and nutmeg on top.