Soak the sultanas in the brandy in covered bowl for at least one hour. But soak for longer if you can - overnight is ideal.
Toast the hazelnuts in a dry frying pan for a few minutes until the nuts brown a little and the skins loosen. Leave to cool, then rub the nuts in a piece of kitchen towel to remove the skins. Roughly chop the clean hazelnuts.
Grate the Jerusalem artichokes. A food processor is probably best for this.
Cream the butter with the sugar until pale and fluffy.
Beat in the brandied sultanas.
Beat in the eggs, one by one, alternating with a little of the flour.
Sieve in the flour, baking powder, bicarbonate of soda, salt and spices.
Stir this in lightly together with the nuts and chocolate.
Fold in the artichokes.
Scrape the mixture into a deep 20 cm (8") lined cake tin and bake for about 50 minutes at 180℃ (350℉, Gas 4) until well risen, brown and an inserted skewer came out almost clean.
Allow to cool in the tin for 15 minutes, then turn out onto a wire rack to cool completely.
Cream Cheese Icing
Beat the cream cheese and sugar together.
Grate in the lemon zest and squeeze in nearly half of the juice.
Beat it all together then slather over the top of the cooled cake.
Shave some dark chocolate over the top to decorate, if liked.
Please note: calories and other nutritional information are per serving. They're approximate and will depend on exact ingredients used.