In a saucepan over medium heat, warm 300ml of the cream with the cinnamon stick, cloves, allspice and orange rind. Remove from the heat right before the cream comes to the boil. Cover and steep for 15 minutes.
Preheat the oven to 170 C / Gas 3. Put the kettle on.
In the same saucepan, pour the spiced cream through a mesh sieve and combine it with the remaining cream. Heat the cream over medium heat until just before it comes to the boil. Remove from the heat and stir in the chopped chocolate until melted and smooth. Allow to cool slightly.
In a mixing bowl, whisk together the egg yolks and the sugar until pale and thick. Slowly whisk in the chocolate mixture.
Place 6 dessert cups or ramekins in a baking dish that's been lined with a tea towel. Divide the chocolate mixture evenly between the 6 ramekins. Add hot water from the kettle so it reaches halfway up the sides of the ramekins. Cover loosely with aluminium foil.
Bake for 15 minutes. They should still be wobbly. Remove the foil and allow to cool at room temperature, then chill until serving, at least 4 hours.