Sift the flour with a pinch of salt into a medium-size bowl and make a well in the middle. Mix the milk and 100ml of water together. Break the eggs into the well and start whisking slowly. Add the milk and water in a steady stream, whisking constantly and gradually incorporating the flour as you do so.
Whisk until the batter is smooth and all the flour has been incorporated. Set the batter aside to rest for 30 mins, then whisk the melted butter into the batter.
Heat the pan over a medium heat. Very lightly grease the pan with melted butter. Using a ladle, pour roughly 2 tbsp of batter into the pan and swirl it around so the bottom of the pan is evenly coated. You want to use just enough batter to make a delicate, lacy pancake. Cook the pancake for about 45 secs on one side until golden and then using a palette knife or fish slice, flip the pancake over and cook the other side for about 30 secs until it freckles.
Slide the pancake out of the pan and either serve immediately or stack on a plate with baking parchment in between. Continue until all the batter is used up.