Melt the butter and warm the milk. Set aside.
75 grams melted butter, 480 grams milk
In a large bowl, whisk the eggs and sugar.
4 eggs, 3 tablespoons sugar
Pour the warm milk over the eggs while whisking.
Add the flour, salt, and vanilla extract, and whisk vigorously using a balloon whisk until you have a smooth batter.
260 grams all-purpose flour, ½ teaspoon salt, 2 teaspoons vanilla extract
Boil the water.
150 ml boiling water
Pour in the melted butter and boiling water over the batter, and whisk again until smooth. Alternatively, you can mix all the ingredients in a blender.
Preheat a 10-inch (26 cm) cast iron skillet on medium heat.
Using a ladle, pour some of the batter, about ¼-⅓ cup, onto the skillet and swirl to evenly coat the bottom. Cook until small holes form on the surface and it starts to brown on the bottom, flip, and cook for 30-60 more seconds until golden. (If the crepes are browning too fast, turn down the heat a bit, or if they are browning too slow, turn it up a notch.)
Place the cooked crepes on a plate and cover with a clean kitchen towel to keep them warm.
Serve with your favorite spread or toppings and enjoy.