1. Preheat oven to 350 degrees. In a medium heatproof bowl, combine egg whites, confectioners' sugar, and pinch of salt. Set bowl over (not in) a pot of barely simmering water and cook, whisking constantly, until mixture is warm and frothy and sugar is dissolved, 1 to 2 minutes. Remove bowl from heat and, using an electric mixer, beat mixture on high until stiff, glossy peaks form, about 3 minutes. Beat in vanilla, then fold in peanuts and chocolate. Transfer mixture to a quart-size zip-top bag; with scissors, cut a 3/4-inch hole in one corner.

2. Pipe 30 mounds (1 inch tall and 1 1/2 inches wide), 1 inch apart, on a parchment-lined rimmed baking sheet. Bake, using the handle of a wooden spoon to keep oven door slightly ajar, until dry to the touch, about 20 minutes, rotating halfway through. Let cool completely on sheet on a wire rack before peeling off parchment.