Think of chocolate Chantilly cream as a really thin ganache — whipped. Yes, you can make chocolate Chantilly cream with cocoa instead, however the cocoa butter in the chocolate makes a nice stabilizer, helping the whipped cream hold its shape. If you wish to supplement the real chocolate with more cocoa powder to boost the chocolate flavor, you can.
Begin by combining a cup of heavy cream with about two ounces of chocolate. These are 70% chips, but just about any chocolate will do.
Zap the mixture in the microwave for about 30 seconds on high and stir, then use as many more zaps of 15 seconds as you need to melt the chocolate completely (stir between each). The mixture will start out looking grainy…
…then smooth out as you re-establish your emulsion. Be advised, the darker the chocolate the more you’ll need to blend the mixture to avoid flecks. I got some as you can see above, but they were small enough that I really didn’t mind them. Use a stick blender to get a perfectly smooth emulsion. Refrigerate the mixture for about 4 hours until it’s quite chilly.
Pour the whole thing into the bowl a mixer fitted with a whip.
And whip to soft or stiff peaks, whichever you prefer. If you want to sweeten the cream along the way, you can do that as well.