First prepare your pancake batter: Combine flour and salt in a bowl. Make a well in the centre. Add the beaten eggs and milk to the well and whisk till smooth. Cover and set aside while you prepare the filling.
Heat the oil in a large wok. Add chicken and brown. Add beansprouts, red pepper, root ginger and garlic, and stir-fry for 2 minutes.
In a small bowl, combine cornflour and soy sauce and mix together; pour mixture into the frying pan, along with the pineapple and juice, vinegar, sugar and ginger. Stir together and bring to a full boil.
While the filling is simmering, prepare the pancakes: Lightly brush a 20cm frying pan with oil and heat over medium high heat. Add about 60ml of batter to the hot pan, and tilt the pan so that the batter spreads evenly over the surface. Cook the pancake for 2 minutes, then flip it over. Cook the second side for about 30 seconds. Repeat with remaining pancakes and stack each on a warm plate between pieces of greaseproof paper.
When the filling is ready, fill each pancake with the filling, fold and place on serving plate. Spoon some of the sweet and sour sauce over each folded pancake, and serve!