Combine the flour and salt in a mixing bowl. In another, smaller bowl, beat together the milk and eggs., Make a well in the flour mixture and pour in about half the liquid mixture. Blend well, then add the remaining liquid and stir until fairly smooth; a few lumps can remain., Stir in the butter. Cover and let sit for at least an hour., Heat a pan until it's medium-hot; a 10" skillet works well here. Use a paper towel to carefully wipe the bottom of the pan with a bit of butter., Pour a scant 1/3 cup of batter into the bottom of the pan. Pick the pan up, and tip it in a circle so the batter covers the bottom of the pan., Cook until the bottom of the crêpe begins to brown and you can slide a spatula under it. It will hold together quite well, so you can flip it over pretty easily. Cook briefly on the other side, just until set, and place on a warm plate. Cover until the remaining crêpes are cooked., Fill as desired. Crêpes can be folded in quarters to eat on a plate, or rolled, burrito-style, for a walk-around snack.