In a blender or large mixing bowl, combine the flour, sourdough discard, eggs, milk, melted butter, salt, sugar and vanilla. Blend or whisk until the batter is smooth and the consistency of heavy cream.
Cover the batter and place in the fridge for at least 1 hour (or up to overnight). This helps make the crepes tender and smooth. Stir gently before using if it looks separated.
Heat a nonstick skillet or crepe pan (8-inch works best) over medium or medium-low heat. Allow it to fully preheat.
Lightly butter the bottom of the pan using a stick of butter before each crepe.
Pour 3 tablespoons of batter into the center of the pan. Immediately lift and swirl the pan in a circular motion to spread the batter into a thin layer.
Let the crepe cook for 1–2 minutes, or until the edges look dry and begin to lightly brown. Let the crepe almost fully cook before flipping so that it doesn’t tear apart.
Flip the crepe and cook the second side for about 1 minute. Transfer to a plate and cover to keep warm.
Repeat with the remaining batter, buttering the pan between each crepe for best results.
Fill or top with your favourite toppings.