1.Grease a long terrine mould,line with plastic wrap and place in the freezer.
2.Preheat your oven to 150C fan-forced or 170C conventional.
3.To make the praline,spread the hazelnuts on a baking tray and roast until lightly golden,about six minutes - the nuts need to be warm when they go into the caramel so don't do this ahead of time (or warm them quickly in the oven if they have cooled down).
4.In a medium saucepan mix the sugar with 30ml of water,bring to the boil and cook to a medium to dark caramel. Be careful with the caramel as it is very hot.
5.Tip the warm nuts into the caramel,stirring thoroughly to coat. Tip the mix out on to a sheet of baking paper and set aside to cool.
6.Put the ice-cream into a large bowl and break it up a little to soften. Crumble 400 grams of the plum pudding (reserve 100 grams to serve) into the bowl and combine. Pack this mix into the chilled mould,pressing down with a spoon and tapping it on the bench to knock out any air pockets. Freezeovernight,or for at least six hours.
7. Mix the chestnut puree with the icing sugar in a food processor until smooth. Spoon into a piping bag and chill. Break up the praline in a mortar and pestle.
8.To serve,gently warm the caramel sauce. Unmould the terrine on to your serving plate,pipe on the chilled chestnut puree,crumble over the reserved pudding,scatter over the praline and spoon over the sauce. Slice with a sharp knife warmed in hot water.
Drink:Sparkling burgundy