Grease and line the base of a 1.2
liter/2 pint
pudding basin. Melt the plain and white chocolate in
separate bowls over simmering water.
Beat together
the butter and sugar until light and creamy.
Gradually beat in the eggs, adding a little flour to
prevent the mixture curdling. Fold in the remaining
flour, then turn half the mixture into a separate
bowl. Stir the plain chocolate into one half and the
white into the other.
Place alternate spoonfuls of
the white and dark chocolate mixtures into the
pudding basin. Level the surface, then swirl a
skewer through the mixtures to marble them together.
Cover the basin with a double thickness of grease
proof paper, securing under the rim with string.
Cover with foil, crumpling this under the rim to
seal.
Cook the pudding in a steamer for
2-2 1/2
hours, topping up with boiling water if necessary.
(Alternatively, position the basin on an upturned
saucer in a large saucepan. Pour water into the pan
to a depth of about 5 cm/2 inches, and cover tightly
Simmer gently.)
Meanwhile, make the sauce. Toast the
hazelnuts in a dry frying pan until they turn a
golden brown. Allow to cool a little and then
roughly chop them.
Heat the sugar and water in a
small, heavy-based saucepan, stirring
until
the sugar dissolves. Bring to the boil and boil
rapidly until caramel-colored. Immerse the base of
the pan in cold water to prevent further cooking.
Add the lemon juice, hazelnuts and butter and heat,
stirring until smooth. Invert the pudding on to a
serving plate and pour over a little sauce. Serve
the remaining sauce separately.