Step 1

Mix cornflour with 2 tablespoons of the reserved cherry juice. Place remaining juice in a pan with sugar over medium-low heat and stir for 2 minutes to dissolve sugar. Add cornflour mixture and stir for 1-2 minutes until sauce thickens. Stir in the cherries and kirsch, then remove from heat and cool. Chill until needed.

Step 2

For the custard, heat milk and cream in a pan over medium heat to just below boiling point. Remove from heat. Whisk egg yolks and sugar in a bowl until well combined. Gradually whisk hot milk mixture into yolk mixture. Return to a clean pan over medium-low heat. With a wooden spoon, stir gently but constantly, for 4-5 minutes, reaching the base and corners, until the custard is thick enough to coat the back of a spoon (when you run a finger along the spoon, it should leave a trail). Remove from the heat. Strain through a fine sieve into a container. Cool for 15 minutes, stirring occasionally. Stir in the jam, cover and chill.

Step 3

Whip the cream with the icing sugar to soft peaks. Slice cake horizontally into 3 even rounds. Place 1 cake layer in a 2-litre serving bowl, trimming to fit if necessary. Spread with half the custard, then top with one-third of the cherry mixture. Repeat this process, then top with the final layer of cake. Top with the whipped cream, then arrange the remaining cherries on top. Chill for at least 2 hours for flavours to develop, then serve garnished with grated chocolate.