Cream of Tartar
I had a about a quart left of already skimmed milk in a half gallon jar and needed to make room for the next milking. I carefully tapped out some cocoa powder from its storage jar, dug out a few large clumps of dark brown molasses sugar with a fork (trying to use it up to make room in the cupboard), tossed in a small spoonful of Cream of tartar and about the same of sea salt. After a dash of vanilla, I put the lid back on and SHOOK, SHOOK, SHOOK. When it looked mostly blended, I poured in in an already frozen ice cream canister and stirred. After about 10-15 minutes, it was frozen and fluffy.
Yeah, I found a few clumps of unmixed, dry cocoa while eating some...but I didn't mind. You could probably do the same thing with chocolate milk made from syrup and avoid the clumps, but I was out. I need to make a double or triple batch next time.