Stir all ingredients until completely mixed. Store in tightly covered container at room temperature up to 6 months.
For each serving: Place 2 to 3 teaspoons mix in cup or mug and fill with 2/3 cup boiling water; stir. Top with whipped cream if desired. For 6 servings, place 1/4 to 1/3 cup mix in heatproof container and add 4 cups boiling water.