Cook the Christmas pudding according to the packet’s instructions, then cool. Alternatively, measure out 130g of precooked leftover Christmas pudding.
Put the cooked pudding in a bowl and mash it up with a fork. Add the booze and the zest, the combine.
Melt the chocolate in a heatproof bowl above a pan of boiling water (the bowl should not touch the water). Let it cool for a few minutes.
Meanwhile, dry-toast the hazelnuts (optional) and, using a small food processor, whiz until you get a coarse crumble.
Add 3 Tbsps of the melted chocolate to the pudding and about 1 -2 Tbsp of the nuts. Combine well. You should get a thick, almost solid mixture. Add more nuts if the mixture is too soft.
Now, using a teaspoon, put a small dollop in your palm and shape a little ball, the size of a chocolate truffle. You should be able to make about 8-10 from the mixture.
Scatter the nuts onto a flat plate. Rotate the balls in the remaining melted chocolate then in the nuts. Put them on a plate, lined with parchment paper.
Put the truffles in the fridge to firm up.
Serve them with coffee at the end of a dinner party or with a glass of fizzy at parties.