Melt butter. Sift the flour and salt into a bowl and stir in the beaten eggs. Add the milk or broth slowly, whisking it in, then add the butter and Parmesan. The batter should be very smooth and the consistency of cream. Let it stand at least an hour or two before making the crepes.
To make crepes heat a crepe pan or small frying pan and melt some butter or oil in it. When the pan is almost smoking, pour in 2 to 3 tablespoons of batter at a time, swirling it around to the edges immediately. Cook for about a minute on each side. Grease the pan a bit between each crepe to avoid sticking. Makes 20 to 24 crepes. Serve with savory fillings.