Heat 12" cast iron frying pan over medium-low burner.
Ladle ¼ to ⅓ cup of batter into heated pan. The amount will on the thickness of your batter. Quickly tilt pan in a circular motion to swirl batter over entire pan and all the way to the edges. If the batter does not spread quickly enough, add a small amount of water and try again with a second crepe. Almost all instructions warn that you probably will need to discard your first crepe.
Allws crepe set approx. 10 seconds and then add filling. In Brittany, home of galattes, many different fillings are used, so experiment.
For a classic filling, first crack an egg in the center, spread the white with the back of a spoon or spatula. Next, sprinkly approx. ⅓ cup grated Gruyère cheese across the surface, and place 2-3 small pieces of thinly-sliced ham around the egg. Season with salt and pepper.
Wait for crepe to crisp and brown on bottom. If you added an egg, cook until the egg is sunny side up.
Fold in the four sides of the galette to create an square with an open center.
Serve and prepare next crepe.