1.Whisk eggs and sugar in a large bowl until combined. Whisk in ground hazelnuts.
2.Place cream in a small saucepan, bring to the boil then remove from heat. Whisk in coffee granules until dissolved. Whisk coffee mixture into hazelnut mixture. Sift flour over hazelnut mixture, stir to combine.
3.Grease a 2-litre (8-cup) pudding steamer. Spoon mixture into steamer. Top with baking paper and foil, secure with kitchen string. Alternatively, cover with a lid.
4.Place pudding steamer in a 4.5-litre (18-cup) slow cooker with enough boiling water to come halfway up side of steamer. Cook, covered, on high, for about 2¾ hours, replenishing with boiling water as necessary to maintain level.
5.Remove pudding from cooker, stand for 10 minutes before turning pudding onto a serving plate. Serve with custard.
To cover pudding, layer a sheet of foil and baking paper together, large enough to cover the top generously. With paper lengthways in front of you, fold a vertical pleat; this will give the pudding space to rise.Note