Sift the flour and salt into a large bowl and make a well in the middle of the flour. Pour the eggs into the well and whisk gently.
Gradually add the milk and water until you have a smooth batter.
Stir in the melted butter and leave to rest for a few minutes, or half an hour if time permits.
Add the vegetable oil to a skillet or non-stick frying pan, wipe out the excess with kitchen paper and add a ladle of batter to the pan.
Swirl the batter around the pan until there is an even layer covering the base of the pan. Fry for two minutes, turn over and fry for a further two minutes on the other side.
Remove the crêpe from the pan and repeat with the rest of batter.
Lay the crêpes on a plate, spread with jam, top with the whipped cream and fold into triangles.
Serve immediately, dusted with icing sugar.