Cut the brioche into thin slices.
Chop white chocolate.
Line the bottom of a buttered dish with a layer of brioche, sprinkle some chocolate on top.
Continue layering the brioche and chocolate until finished.
Whisk together the egg, egg yolks and sugar.
In a saucepan mix single cream/half and half with the spices and vanilla, heat until just simmers.
Pour 1/2 cup of hot cream into the egg mixture while whisking the whole time. Add the remaining cream, continue whisking.
Pour the eggnog custard over the brioche and let stand for 5 minutes, then lightly press the brioche slices into the cream mixture.
Place the baking dish in a roasting pan and pour boiling water into the pan so it comes halfway up the side of a baking dish.
Bake in the preheated oven at 350F/180C for 30-40 minutes until the pudding has risen a bit and the eggnog custard is set.
Serve warm with additional cream.