There is a recipe for hot chocolate mix in the recipe forums...check it out!
Otherwise, yes, you should be able to, as long as your mix doesn't have anything that says, "partially hydrogenated", but be aware that it counts as part of your 75 cals of sweet treats. I know the kind we have here is 60 cals...so it doesn't leave me much in the way of desserts!
How about tea? There are some decadently delicious herbal flavors out there that you can have with a bit of splenda (or even without!) and are decaf. Or decaf regular teas...I found a decaf Caramel Creme that I have with a splash of 2% milk...yum!
And The Republic of Tea makes a great "Red Tea" (Rooibos herb tea, has more antioxidants than green tea, but is caffeine free!) called "Good Hope Vanilla" which has a taste of creme and vanilla in it...yummy! There is also the option of getting a decaf latte with 2% or skim milk and some sugar free syrup. Lots of options that don't spend your sweet treats!
