Combine the milk, water, eggs, flour, and salt in a blender. Blend on medium speed for 15 seconds, until the batter is smooth and lump-free. Scrape down the sides of the blender and pour in 3 tablespoons of melted butter. Blend it again for a second just to incorporate. Refrigerate the batter for 1 hour to let it rest. If the crepes are made immediately, they have a tendency to be rubbery; when you let the batter rest, the crepes have a better texture and a softer bite.
Put an 8-inch crepe pan or nonstick skillet over medium heat and brush with a little melted butter for added insurance. Pour 1/4 cup of batter into the pan and swirl it around so it covers the bottom evenly; pour back any excess. Cook for 30 to 45 seconds, until the crepe batter sets. Lightly bang the edge of the pan with a wooden spoon to loosen the crepe; then flip it and cook another 30 seconds. The art of flipping a crepe in the air takes practice, so make sure no one is looking when you get the first one going. If this intimidates you, use a heatproof rubber spatula to loosen and flip the crepe. The crepes should be pliable, not crisp, and lightly brown. Slide them onto a platter and continue making the crepes until all the batter is used. Cover the stack of crepes with a towel to keep them from drying out.
Edited: October 14th, 2009