In a medium bowl, whisk together the flour, sugar (if using), and salt until evenly combined.
In a separate bowl, beat the eggs; add the milk, melted butter, and vanilla; whisk until smooth.
Slowly pour the wet mixture into the dry ingredients while whisking to avoid lumps.
Cover the bowl and let the batter rest at room temperature for 30 minutes.
Heat a nonstick skillet over medium heat; lightly brush with butter or oil.
Pour roughly ¼ cup of batter into the center of the skillet, swirling to spread a thin circle.
Cook until the edges lift from the pan and the underside is golden, about 30–45 seconds.
Flip and cook the second side for 15–30 seconds until lightly golden.
Transfer the crêpe to a plate and keep warm; repeat with remaining batter.
Fill, fold, or stack with desired fillings and serve immediately.
