Place flour, milk, eggs, and salt in a blender. Add butter and pulse until smooth, about 20 seconds. Batter should be the consistency of heavy cream. Transfer to a bowl; cover and refrigerate for 30 minutes to 1 hour.
Heat a 6-inch nonstick skillet over medium heat. Lightly brush skillet with olive oil. Ladle 2 to 3 tablespoons of batter into the hot pan, quick