For the pancakes, first beat the eggs well, add the flour, salt and milk. Whisk until hearty and smooth. Gradually add enough mineral water to make a very thin batter. Allow to swell for 1/2 hour.
Coat coated or cast iron frying pan with a little fat (light butter, butter, clarified butter, oil). Let the frying pan get very hot. Pour in a small ladleful of batter at a time and swirl on the spot to quickly spread it all over. Toast over medium heat until golden brown on both sides. As soon as the outer edge curls, turn the pancakes to the other side using a palette and finish baking.