Coarsely chop the chocolate with a sharp chef’s knife. Or use chocolate chips. Place the chocolate and butter in a shallow microwave-safe bowl. Microwave it in two 30-second sessions, stirring after each session, until the chocolate is almost melted.
Stir in the heavy cream. Microwave for 20 more seconds, then stir the mixture with a rubber spatula until it turns into a smooth ganache, as shown in the video below. You can stir in a bit of stevia at this point if you'd like.
Cover the mixture with a plastic wrap and freeze for 30 minutes.
Now comes the fun (and messy!) part, so you might want to use disposable gloves: Scoop out small portions of the mixture, measuring about 1 tablespoon per truffle. Shape the truffles with your hands into balls. They won’t be perfectly round.
Roll the truffles in the cocoa powder to coat. They're ready! Enjoy.
The only somewhat challenging part when making these truffles is shaping them. This is quite messy, so I highly recommend that you wear disposable gloves when performing this task.It's not that it's difficult to wash your hands and get rid of the chocolate, but it does tend to get under your nails.