Combine Ingredients: In a blender, combine the flour, eggs, milk, salt, melted butter, and sugar/vanilla (if using). Blend on high speed for 30-45 seconds until the batter is completely smooth and no lumps remain. Alternatively, whisk vigorously by hand in a large bowl.

Rest the Batter: Let the batter rest at room temperature for at least 30 minutes. This allows the gluten to relax and results in more tender crepes. For best results, cover and refrigerate for up to 1 day.

Heat the Pan: Heat a medium-sized non-stick skillet or crepe pan over medium heat. Lightly grease the pan with a small amount of butter using a paper towel.

Cook the Crepe: Pour about ¼ cup of batter into the center of the hot pan. Immediately lift the pan from the heat and tilt it in a circular motion to swirl the batter into a thin, even layer that coats the bottom.

Set and Flip: Cook for 1-2 minutes, until the edges begin to lift and the bottom is lightly golden. Carefully slide a thin spatula under the crepe and flip it. Cook for another 30-60 seconds on the second side until lightly spotted. Transfer to a plate.

Repeat: Repeat with the remaining batter, regreasing the pan with butter every 1-2 crepes as needed.

Serve: Serve immediately with your favorite fillings and toppings. Crepes can be kept warm in a low oven (200°F/95°C) on a baking sheet.