Vanilla bean pastry cream meets white butter cake in this take on the French classic by Wendy Kromer.
To assemble the cake: Split the two cake layers in half, horizontally. Set one layer on a corresponding-size cardboard round, and pipe a dam of caramel buttercream around the edge of the layer, then fill with vanilla-bean pastry cream. Set next cake layer on top, and spread with approximately 2/3 to 3/4 cup of the caramel buttercream. Set the next cake layer on top, pipe a dam, and fill with pastry cream. Set the last cake layer on top, then crumb-coat tier using caramel buttercream. Chill the cake layer well, then spread on another layer or two of caramel buttercream, giving the tier a final coat.