Beat the eggs and milk together until frothy.  Add the salt and flour, 1/4 cup at a time, and beat until no lumps can be found.  The batter should be the consistency of heavy whipping cream.  

Place a crepe pan, over medium-high heat.  Brush lightly with some of the melted butter.  Hold the crepe pan with one hand off the heat, pour 1/4 cup of batter in the center, and quickly but gently swirl, tilting the pan at an angle in a circular motion, as you're pouring, until the batter covers the whole surface of the pan in a thin layer.  

Reduce the heat to medium, and after approximately 1 minute, flip the crepe, using a thin spatula.  Watch the edges of the crepe, and as they color a little, it's a sign the crepe is ready to be flipped over.  With the spatula tip, gently go around the edge of the crepe, trying to separate it from the pan. If you can do this effortlessly, it's time to flip. Continue cooking the crepe on the other side for another 30 seconds or so.  

Remove the pan from the heat, and brush lightly with butter ( I use a stick, and just rub it gently over while the crepe is still hot).  

Brush the pan again with the melted butter, and continue in the same manner with the rest of the batter.  You may need to adjust the heat until you find the optimal heat level.  The first crepe may be a bit different due to the heat being either too high or too low.  As you continue to make the crepes, they will be more uniform.  

Place the crepe pan back over medium heat.  Add about 1-2 tsp of sugar to the pan, distributing it as evenly as possible, and a small knob of butter.  When the sugar begins to melt and caramelize, sprinkle a few flakes of coarse sea salt, and place a crepe on top.  Wait for 10-20 seconds and remove the crepe, flipping it on a plate with the caramelized side up.  Wait until it cools off, and crisps up, before serving.