Blood plums and chocolate pair really well, and for this trifle it's worth splurging out on really great dark chocolate. The plums' lovely tartness cuts through the rich crémeux and we've added Scotch for the boozy kick.
Note Umeshu is a Japanese liqueur made from ume, an apricot; it's available from Asian grocers. We used Caraïbe Noir, a 66% cocoa solid grand cru blended chocolate by Valrhona; it's available from Simon Johnson. If it's unavailable substitute a good chocolate with 63%-68% cocoa solids.