1.Grease six 1-cup (250ml) ovenproof dishes.
2.Cut panettone into 1.5cm-thick rounds; spread one side of each round with butter. Cut each round into quarters; divide among dishes.
3.Preheat oven to 160°C.
4.Combine milk and vanilla bean in medium saucepan; bring almost to a boil. Remove from heat; stand, covered, 10 minutes.
5.Meanwhile, whisk eggs and half of the sugar in large heatproof jug. Gradually whisk hot milk mixture into egg mixture. Strain into large jug; discard vanilla bean.
6.Carefully pour egg mixture over panettone in prepared dishes. Place dishes in large baking dish; add enough boiling water to come halfway up sides of dishes. Bake, uncovered, about 30 minutes or until set.
7.Meanwhile, place nuts on oven tray; toast, uncovered, in oven with panettone about 10 minutes or until browned lightly.
8.Place remaining sugar and the water in small saucepan; stir over heat, without boiling, until sugar dissolves. Boil, uncovered, without stirring, about 10 minutes or until sugar syrup is golden brown; pour over nuts. Cool; chop toffee coarsely.
9.Serve custards topped with toffee; dust tops lightly with icing sugar.
Brioche, hot cross buns or fruit loaf can be substituted for the panettone.Note