Prepare the Batter:

1. Put the water, milk, eggs, and salt into blender or food processor. Add the flour, then the butter. Cover and blend at top speed for 1 minute. If bits of flour adhere to the sides of the blender, scrape down sides with rubber spatula and blend for a few seconds more. Cover and refrigerate for at least 2 hours, or overnight. (Note: The batter should be a very light cream, just thick enough to coat a wooden spoon If, after making your first crêpe, it seems too heavy, beat in a bit of water, a spoonful at a time. Your cooked crêpe should be about 1/16 inch thick.)

Method for Making Crêpes:

1. Brush or spray skillet or crêpe pan with cooking oil. Set over medium-high heat until the pan is just beginning to smoke.
2. Immediately remove from heat and, holding handle of pan in your right hand, pour with your left hand a scant 1/4 cup of batter into the middle of the pan. Quickly tilt the pan in all directions to run the batter all over the bottom of the pan in a thin film. (Pour any batter that does not adhere to the pan back into your bowl; adjust the amount for your next crêpe accordingly.) This whole operation takes 2 to 3 seconds.
3. Return the pan to heat for 60 to 80 seconds. Then jerk and toss pan sharply back and forth and up and down to loosen the crêpe. Lift its edges with a spatula and if the under side is a nice light brown, the crêpe is ready for turning.
4. Gently, using a spatula or by grasping the edges with your finger, turn the crêpe over and brown lightly for 30 seconds.
5. As they are done, slide the crêpes onto a rack and let cool several minutes before stacking on a plate.
6. Grease the skillet again, heat to just smoking, and proceed with the rest of the crêpes.