First mix the milk and water together.
Then sift the flour and salt into a large mixing bowl. Make a well in the centre of the flour and break in the eggs.
Using an electric whisk or a balloon whisk, whisk the eggs into the flour gradually adding the milk and incorporating the flour from around the edge of the bowl. Scrape any remaining flour down from around the sides of the bowl with a rubber spatula and whisk again until all the mixture is smooth. It should be the consistency of thin cream.
Spoon 2 tablespoons of the melted butter into the batter and whisk again. Reserve the remaining butter.
Let the mixture stand for 20 minutes.
Place five plates in a warm oven.
Get the pan/skillet really hot, then turn the heat down to a medium setting.
Smear a little of the reserved butter over the base of the pan/skillet between cooking each pancake.
You will need about 3 tablespoons of batter for each pancake. It is easier to measure this into a ladle or measuring cup first. Then pour the batter quickly into the centre of the pan/skillet, at the same time tipping the pan/skillet around from side to side to get the base evenly coated. If there are any holes, just fill them in with extra batter using a teaspoon. It should take less than a minute for the underside to turn golden. Check by lifting the edge with a palette knife.
Flip the pancake over with the palette knife and cook the other side until golden. This side will need less time to cook. Then slide it out of the pan onto a warmed plate.
Continue making the pancakes until all the batter is used. Stack them on the warmed plate as they are ready. Keep them warm in the oven, covered loosely with foil.
To serve, fold each pancake into quarters and divide them amongst the four warmed plates. Pour the lemon juice over the pancakes and then generously sprinkle with sugar.