I have found that when adding cocoa to a beer, you want to make a paste like Oldstock says, though if you use an alcohol (I use creme de cacao for even more chocolate), the cocoa goes into solution more readily compared to water where it tends to be in suspension.
Primary 1:French Fantom (Saison with Fatome Saison blend)
Primary 2: Columbus/Simcoe IPA
Primary 3: Belgian Tripel
Up next: Tangerine Wit, Flanders Red, Maybe a Gose?