Editor's note: The recipe and introductory text below are from David Lebovitz's The Perfect Scoop: Ice Creams, Sorbets, Granitas, and Sweet Accompaniments. To read Epicurious's review of the cookbook, go to Summer Cooking Guides.
This is the perfect chocolate sorbet — very rich and full of bittersweet chocolate flavor. Use a top-quality cocoa powder; it will make a huge difference. And be sure to use a large saucepan, since the mixture will bubble up as it boils.