Chill 55g of white chocolate in the fridge for easier grating later.
Cream the egg yolks and caster sugar together in a large bowl for 3 minutes until thick.
Boil 150ml milk and 85g cream in a saucepan, then whisk into the egg mixture.
Heat the mixture while stirring until it thickens, then incorporate the remaining chocolate pieces.
Cool the custard slightly and cover with icing sugar and cling film to prevent skin.
Place swiss roll slices in a glass bowl, sprinkle with Kirsch, and add most of the raspberries.
Pour the custard over the cake and refrigerate overnight to set.
Garnish with reserved raspberries and grate the chilled 55g of white chocolate over the top.
Dust with icing sugar and garnish with fresh mint sprigs.