Instructions

1. Make the dark chocolate custard: Whisk together 1⁄2 cup sugar, 2 tbsp. cornstarch, and 1⁄4 tsp. salt in a 2-qt. saucepan; add 2 egg yolks and 1 egg and whisk until smooth. Add 2 cups milk and heat over medium heat. Bring to a boil, stirring often, and cook until mixture thickens, 1-2 minutes. Remove from heat and add dark chocolate in four batches, whisking after each addition until smooth. Add 2 tbsp. butter and 2 tsp. vanilla and whisk until smooth; transfer to a bowl, cover surface with plastic wrap, and refrigerate dark chocolate custard until chilled.
2. Make white chocolate-blueberry custard: Whisk together remaining sugar, cornstarch, and salt in another 2-qt. saucepan; add remaining egg yolks and egg and whisk until smooth. Add remaining milk and heat over medium heat. Bring to a boil, stirring often, and cook until mixture thickens, 1 to 2 minutes. Remove from heat and add white chocolate in four batches, whisking after each addition until smooth; add remaining butter and vanilla and whisk until smooth. Transfer to a bowl and cover surface with plastic wrap; let cool to room temperature. Fold blueberries into white chocolate custard and set aside.
3. Assemble trifle: Cut half of Ginger-Lingonberry Cake cake into 1" cubes (reserve remaining cake for another use). Arrange cake cubes snugly in bottom of a 3-qt. glass trifle dish or bowl; drizzle with 2 tbsp. sherry. In a medium bowl, toss raspberries with kirsch and add to the top of the cake in a single layer. Spoon white chocolate custard over raspberries and smooth top with a rubber spatula; refrigerate until set, 30 minutes. Meanwhile, heat the raspberry jam in a small saucepan over medium heat until loose; pour through a fine strainer set over a small bowl and let cool for 10 minutes. Pour jam over white chocolate custard and spread evenly. Return trifle to refrigerator and chill until set, 2 hours. Stir dark chocolate custard until smooth, spoon over jam, and smooth with spatula; cover dish with plastic wrap; chill for 8 hours.
4. An hour before you plan to serve trifle, make syllabub: Whisk together sugar, 1 tsp. sherry, cognac or brandy, and lemon zest in a large bowl until sugar dissolves. Add cream and whisk until mixture holds peaks but is not stiff; spoon syllabub over dark chocolate custard, creating swirls and peaks with spoon, and chill until ready to serve.