This decadent chocolate cake has a pillowy, not-too-sweet peanut butter frosting that has garnered me much attention at her school. Even years later, parents have come to me to talk about the cake.

Bake cake until it springs back when gently pressed or a tester inserted into the center comes out with a few moist crumbs attached, 25–30 minutes. If serving cake directly from pan, let cool in ...