Mix the flour with the milk. Add the eggs and stir in the salt. Melt the butter and add it. Mix everything into a creamy, slightly runny batter. Place the dough in the refrigerator for about 1 hour to swell.
Heat up a crepe pan and add a ladle of batter. Spread the dough evenly in it. When the batter is dry and bubbling, turn it over. Take the crepe out of the pan and continue processing.