Mascarpone is an Italian cheese similar to cream cheese minus the tang. Its buttery richness really shines in this cake, and we found in testing that cream cheese just didn’t compare. Mascarpone can be expensive, so shop around. (Locally, we’ve found the best prices at Trader Joe's.)
Vanilla bean paste is available online or at specialty stores. (Nielsen-Massey is a reliable brand.) Use it in pale desserts where you want to see telltale specks of vanilla seeds.