This is so wonderfully rich and chocolatey! Better than chocolate ice cream, in my opinion. Make sure you use a large pot or it will bubble over. And don't skip the blender step--I did, and while it was wonderful, there were little bits of chocolate and I think it would be even better perfectly smooth.
from The Perfect Scoop
2 1/4 cups water
1 cup sugar
3/4 cup unsweetened cocoa powder
Pinch of salt
6 ounces (170 g) bittersweet or semisweet chocolate, finely chopped
1/2 teaspoon vanilla extract
In a large saucepan, whisk together 1 1/2 cups of the water with the sugar, cocoa powder, and salt. Bring to a boil, whisking frequently. Let it boil, continuing to whisk, for 45 seconds.
Remove from the heat and stir in the chocolate until it’s melted, then stir in the vanilla extract and the remaining 3/4 cup water. Transfer the mixture to a blender and blend for 15 seconds. Chill the mixture thoroughly, then freeze it in your ice cream maker. If the mixture has become too thick to pour into your machine, whisk it vigorously to thin it out. After freezing in the ice cream maker, transfer to another (cold) container to continue freezing until it's the right consistency (another hour or so).
You can probably make this without an ice cream maker--just put it in the freezer and stir every half-hour or so until frozen--probably 4 hours?
Makes 1 quart.