Preheat oven to moderate, 180°C (160°C fan-forced).

Halve cucumbers lengthways; remove seeds. Slice the cucumber and green onions into thin, 8cm-long strips.

Place duck in a baking dish, cover with foil; heat in a moderate oven for about 10 minutes or until duck is hot.

Meanwhile, sift the flours into a bowl; whisk in the combined egg, milk, water and oil until smooth. Transfer mixture to a jug.

To make pancakes, add 1 tablespoon of batter, in batches, to a dry, non-stick frying pan; cook over a medium heat until browned lightly on both sides. Wrap pancakes in foil as they are cooked to keep warm and prevent drying out. Or, to steam pancakes, line a bamboo steamer with baking paper. Place steamer in a wok of boiling water. Steam pancakes, covered, in batches, for about 2 minutes or until soft.

Spread each pancake with 2 teaspoons of hoisin sauce; top with the cucumber, onion and duck. Roll up to enclose filling.