Dough: Boil some water and into a large mixing bowl add the flour, salt and 250ml of boiling water. Stir the mixture with a fork then add the egg and the cold water incorporating the dry flour on the sides of the bowl, until a ball of dough forms. Leave for 15 minutes to rest in the bowl, covered with a kitchen cloth. Turn the dough out onto a floured surface and knead for 1-2 minutes until smooth (the dough will be slightly sticky). Brush with oil to prevent it from drying out, then cover and let rest for at least 30-60 minutes or chill overnight in the fridge for the best results.
Oil paste: In a small saucepan, heat 100ml of oil. Slice the spring onions and place them in a heat-resistant bowl along with the flour. Once the oil is hot, carefully pour it over the onion and flour mixture (oil will sizzle a little), stir to form a thin paste.
Roll dough: Divide the dough into 8 equal portions, roughly weighing 100g each. Place all but one piece back into the bowl and cover. On a lightly oiled surface, roll out the first portion into a thin rectangle.
Spoon or brush an even layer of oil paste over the rectangle dough.
Roll up the rectangle from the bottom to the top.
Coil it right to left (snail-style) to form a circle, tucking the end securely in.
Flatten gently with your palm and then roll each coil into a thin circle with the rolling pin.
Repeat with the remaining dough portions.
Cooking: Brush a non-stick pan with a little oil and place over a medium low heat. Lay one jianbing inside the pan, cover with a lid and cook for 3 minutes, or until the bottom is golden. Then flip it over, cover again and cook for another 2 minutes.
Remove the lid and roughly push the sides of the jianbing with two spatulas to loosen the layers. Flipping once or twice until the pancake is crispy and a deep golden brown.
Brush the pan with a new layer of oil and repeat with the remaining jianbang.
Serve plain or with a dipping sauce.