Place a fine-mesh sieve over a large mixing bowl, and sift all ingredients into the bowl. Mix well with a rubber spatula or whisk (but slowly because it's very powdery!).
If this is your first time making it, taste test your mixture to be sure it is to your liking. Depending on the size of your mug, use 3-4 Tablespoons and mix with hot water. If you'd like your mixture more or less sweet, either add cocoa (to make it less sweet) or add more sugar. Mix well, test again.
When you are happy with your mix, scoop it into air-tight containers for keeping.
For a cup of cocoa: Use 3-4 Tablespoons of the mix in hot water. Add a splash of cream, creamer, or half-n-half for an extra creamy taste. And enjoy!