Finely grate the bittersweet chocolate. Place the milk powder, grated chocolate, and cayenne pepper, to taste, in a large mixing bowl and combine thoroughly. Spoon the mixture into attractive tins or jars and tie the cinnamon stick to the jar. Label the jar with the following instructions:
Use 1/2-cup of chocolate mixture with each cup of hot milk or water. When making the hot chocolate, be sure to boil the chocolate milk for at least 15 seconds. Use the cinnamon stick to stir. Serving with marshmallows is optional.