Combine the milk, eggs, salt, sugar and butter in a blender and process until smooth. Add the flour all at once and blend only until it is completely incorporated. If you see any lumps remaining in the batter, strain it through a fine strainer.

Refrigerate the batter for at least 2 hours to let it rest. This will help prevent lace-y crêpes. (*Upon further research, I've tried making crêpes without resting the batter and have not had any trouble cooking them. I do, however, believe that the flavor continues to improve over time, so if you have time to rest the batter, do it. If you don't have time, skip it.)

Pre-heat a 10-inch skillet or crêpe pan over medium heat.

Brush the pan with a little melted butter and then pour in enough batter to just cover the bottom of the skillet. If you have any excess batter in the pan, pour it back out into the batter bowl. (Measuring with a ¼ cup measure is a great way to be consistent.)

Reduce the heat to medium and cook the crêpe for 1 minute on one side. Loosen the edge of the crêpe with a silicone spatula and then grab the edge with your fingers, lift it out of the pan and flip it over. Cook for another minute on the second side and then turn it out of the skillet onto a plate.

Repeat for as many crêpes as you need, or until you run out of batter, monitoring the temperature under the pan to keep the crêpes from burning or not cooking quickly enough.