In a large bowl, whisk together the flour, sugar, and salt.
Add the eggs and about half of the milk. Whisk until no lumps remain.
Slowly add the rest of the milk, melted butter, and vanilla (if using). The batter should be thin and smooth, almost like heavy cream.
Let the batter rest for 10–15 minutes. This helps the flour absorb the liquid and makes the crepes softer.
Heat a nonstick skillet over medium heat and lightly brush with butter.
Pour about ¼ cup of batter into the centre, quickly tilting the pan to spread it evenly.
Cook for about 1–2 minutes until the edges start to lift and the bottom is lightly golden.
Flip gently with a spatula and cook for another 30 seconds.
Stack finished crepes on a plate and keep them warm under a towel.