For the custard, put the orange juice in a heatproof bowl and microwave for 30 seconds, or warm in a pan over medium heat, then add the cranberries. Remove from the heat and leave to soak until plump.

Warm the milk and cream in a pan with the orange zest over a medium heat until it starts to steam but not boil. Meanwhile, beat the eggs, sugar and vanilla in a bowl, then pour the steaming milk over, stirring constantly. Set aside to cool.

Lightly butter a deep, 1-litre baking dish. Slice the challah into around 10 slices, and remove the crusts. Butter on both sides.

Arrange a third of the challah in the baking dish and scatter over a third of the chocolate chips. Drain the cranberries, add the juice to the custard, then scatter a third of the cranberries over the challah. Pour over a third of the custard, top with half the remaining challah and half the remaining cranberries and chocolate chips. Pour over half the remaining custard and leave to soak for at least 1 hr. Repeat with the remaining ingredients, then chill for at least 4 hrs, or overnight.

Heat the oven to 180C/160C fan/gas 4. Sprinkle over the demerara sugar, bake for 30 mins or until golden, leave to stand for 10 mins, then serve with crème fraîche.