Put the flour and salt in a bowl. Make a well. Pour in the slightly beaten eggs into the well. Stir with a fork until mixed.
Stir in the rum. Add the milk slowly, stirring constantly with a fork. The batter should be smooth, so any lumps need to the broken up and blended inches Let the batter sit for 30 minutes before proceeding.
Brush a crepe or heavy frying pan (any size) with melted butter.
When the pan is hot, pour in just enough batter to thinly cover the bottom of the pan. Tilt the pan so the base is completely covered with batter. Cook crepe until golden on the bottom (1 minute or so). Flip with a metal spatula, and cook until the second side is golden.
Transfer crepe to a plate and cover with foil to keep warm.
Repeat the cooking process until the batter is used.
Unfilled crepes can be well wrapped and frozen.
The recipe can be halved, but then use only two eggs.