Mango and Lime Chiffon Cake

Whisk sugar, lime juice, egg yolks, 3 whole eggs, and grated ginger in large metal bowl to blend. Set bowl over saucepan of simmering water (do not allow bottom of bowl to touch water). Whisk constantly until mixture thickens and instant-read thermometer inserted into mixture registers 160 °F, about 6 minutes. Remove bowl from over water. Quickly add chilled butter cubes to curd; whisk until butter is melted. Press sheet of plastic wrap directly onto surface of lime-ginger curd; refrigerate curd overnight. (Lime-ginger curd can be made 3 days ahead. Keep covered and refrigerated.)