Melt the butter: Place a 7-inch skillet over medium heat. Add 1 tablespoon butter and let it melt without browning. Pour the melted butter into a small cup, leaving a little in the skillet to help prevent sticking.
Make the base: In a medium bowl, combine 1/3 cup flour and 1 egg. Add a few tablespoons of the milk, along with the salt and sugar. Whisk until completely smooth and no dry flour remains.
Add the remaining milk: Slowly whisk in the rest of the 1/2 cup milk. Continue whisking until the batter becomes very thin and pourable, similar to light cream.
Add the butter: Whisk the melted butter into the batter. Add a small splash of water when needed to loosen the batter. The finished batter should flow easily from a spoon or whisk.
Cook the first crêpe: Return the skillet to medium heat. Pour about 1/4 cup batter near one side of the skillet. Quickly tilt and shake the skillet so the batter spreads into a thin, even layer.
Cook the first side: Cook for about 1 minute, watching the edges. They should look set and the underside should be lightly golden.
Flip: Slide a thin spatula underneath the crêpe and gently turn it over. Cook the second side for about 30 seconds.
Finish the remaining crêpes: Transfer the cooked crêpe to a plate and repeat with the remaining batter. Use about 1/4 cup batter for each crêpe.
Serve: Keep the browned side facing up. Fold or roll the crêpes while warm and serve immediately for the softest texture.
