Using a peeler, remove the skin of the orange, then juice the orange and keep aside.
Toast all the spices in a pan over low heat just until fragrant.
Place 250ml of the wine in a saucepan with the zest, sugar and spices and bring this to a boil then reduce to a syrup.
Add the orange juice and the rest of the wine, bring this up to a boil again then cover and allow to infuse for 10 minutes.
Strain into another container then put it back into the pot and bring to a simmer.
Remove from the heat and whisk in the chocolate
Serve hot with marshmallows (optional)