The frosting, from Better Baking by Genevieve Ko, is as simple to make as the ingredient list suggests. Simply bring the sweet potato purée to a simmer in a large saucepan, remove from heat, add the dark chocolate, and stir until smooth. Let it cool, stirring occasionally, until the frosting is at room temperature and the same consistency of canned frosting (but so, so much better). And, look! You can watch how to make it.
If you go to the recipe, you'll see this frosting is meant to accompany a chocolate-zucchini cake. And while you could spread it over the cake, "creating swoops and swirls," as Ko suggests, the two-ingredient frosting is no one-cake wonder: Use it in place of any other (far more complicated) frostings, swap it out for a glaze, or dollop it on top of a slice of poundcake or similar loaf-like things. Here are some ideas to get you started:
Although we've yet to try it (soon!), you could swap the sweet potato purée for pumpkin or butternut squash purée and the semisweet or dark chocolate for milk chocolate. The swoops and swirls, though? Those are less optional.
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What kind of cake/cupcake/loaf/etc. would you put sweet potato frosting on? Let us know in the comments below!