To make the batter, lightly whisk the egg, milk and salt together in a bowl. Whisk in the flour, a little at a time, until the batter is the consistency of thin custard. Leave to rest for 30 minutes. Strain the batter, if there are any lumps. Stir through the chives.
Heat a small, heavy-based frying pan over medium heat. Brush the pan with the butter and pour in just enough batter to form a 10 cm (4 inch) pancake. Cook for 1–2 minutes or until golden, then flip over and cook the other side until golden. Remove from the pan and repeat with the remaining batter.
Preheat the oven to 180°C (350°F/Gas 4). Place the duck on a baking tray and bake for 8–10 minutes or until just heated through. Remove and thinly slice.
To serve, gently warm the pancakes in the oven. Lay the pancakes on a surface and spread with a little hoisin sauce. Place 1–2 slices of duck, some lettuce, cucumber and coriander leaves in the centre of each pancake and roll up. Serve with extra hoisin sauce for dipping.
MAKES ABOUT 20
200 g (7 oz) pre-cooked duck breast, skin discarded
hoisin sauce, for spreading and dipping
¼ iceberg lettuce, shredded
1 Lebanese (short) cucumber, cut into long, thin strips
1 cup coriander (cilantro) leaves
PANCAKES
1 egg
250 ml (9 fl oz/1 cup) milk
pinch of salt
150 g (5½ oz/1 cup) plain (all-purpose) flour
1 tablespoon snipped chives
30 g (1 oz) butter, melted