In a deep, flat bottomed bowl crack the egg, pour in the cream and whisk well until all combined.
Add all the spices and the caster sugar and mix well.
Lightly zest the orange, you just want the top layer of peel and none of the white as this is bitter.
Add the zest to the mix.
Place the 2 brioche slices into the mix and leave for 1 minute, if they don't quite fit into your bowl you can cut them in half and arrange them to fit if possible.
After 1 minute turn over for the other side to soak up the mixture.
Gently move the slices around so they have totally absorbed as much of the mixture as possible.
In a shallow frying pan melt the knob of butter on a low-medium heat.
Place the soaked brioche into the pan and cook for 3 minutes or until golden, then flip and repeat on the other side.
Once cooked through and golden brown, serve on a plate and sprinkle with a light dusting of icing sugar and dark chocolate.
Eat straight away.