Inspired by Hervé This’ one-ingredient chocolate mousse, this Big Little recipe takes two pantry staples and turns them into a fluffy cloud—all thanks to water (and some elbow grease). Flaky salt on top is optional, but highly recommended. Note: This recipe calls for sweetened peanut butter, which gets along better with the water; unsweetened peanut butter is more likely to separate. —Emma Laperruque
Make the peanut butter mousse: Add the peanut butter to a small mixing bowl. Add a small splash (figure about 2 tablespoons) of the water and mix with a fork until cohesive. Repeat this (splash, mix, splash, mix) until you’ve added all the water. The peanut butter should be fluffy and smooth, almost like frosting.
Make the chocolate mousse: First, set up an ice bath by adding ice (crushed is best) to a large bowl and setting a slightly smaller bowl on top of the ice.
Now, combine the chocolate and water in a smallish saucepan and set over the lowest heat possible. Stir constantly until most of the chocolate is melted. Cut the heat and continue to stir until all the chocolate is melted.
Pour the chocolate-water mixture into the bowl on top of the ice. Start whisking like your life depends on it. You’ll do this for 4 to 6 minutes until you’ve reached the consistency of a very loose chocolate pudding—not like whipped cream, which means you’ve gone too far. The whisk should leave distinct trails while in motion, but then once you stop whisking, those trails will barely hold. The best way to avoid over-whipping is to stop and check its progress frequently.
When the chocolate mousse is ready, layer the mousses together. (If you try to swirl one into the other, they’ll become homogenous before you can say “dessert,” so this is the easiest way to avoid that. And if the peanut butter mousse has started to separate at all, just stir it until it's smooth again.) Add about one-third of the chocolate mousse to a large bowl. Add about one-third of the peanut butter mousse on top, in big random spoonfuls. Add about half the remaining chocolate mousse on top, also in big random spoonfuls. Add about half the remaining peanut butter mousse on top in the same way. Repeat with the rest of the chocolate mousse, then the rest of the peanut butter mousse.
Use spoons or an ice cream scoop to portion the chocolate–peanut butter mousse into six dishes (I like using dessert coupes).
Sprinkle with flaky salt. This is best served immediately, but you can refrigerate any leftovers for later, too.
Emma is the food editor at Food52. Before this, she worked a lot of odd jobs, all at the same time. Think: stir-frying noodles "on the fly," baking dozens of pastries at 3 a.m., reviewing restaurants, and writing articles about everything from how to use leftover mashed potatoes to the history of pies in North Carolina. Now she lives in Maplewood, New Jersey with her husband and their cat, Butter. Stay tuned every Tuesday for Emma's cooking column, Big Little Recipes, all about big flavor and little ingredient lists. And see what she's up to on Instagram at @emmalaperruque.