Add flour, salt, milk, eggs, and vanilla to a blender. Blend until smooth. Pour the butter in through the top and continue to blend for another minute. 

Pour into a bowl or pitcher and cover. Keep in the fridge overnight. (Or at least an hour.)

When you are ready to make your crepes, let the batter sit out for about 30 minutes to lose the chill from the fridge. Heat a crepe pan or a 10-inch nonstick sauté pan over medium-high heat. Wipe the pan with a little vegetable oil or melted butter. (I keep an oiled paper towel nearby.

Pour a 1/4 to a 1/3 cup batter into the center of the pan. Pick the pan up and swirl the pan until the batter spreads and covers the pan. Cook until the bottom begins to brown. Loosen with a spatula (I like to use an offset spatula for this) and flip to cook the other side. 

Serve with strawberries, Nutella, whipped cream, sliced almonds, cinnamon sugar, caramel sauce, or whatever you like on your crepes.