1. In a large bowl or blender, combine the flour, salt, sugar, eggs, warmed milk, water, melted butter, and vanilla extract (if using). Whisk or blend until the batter is smooth and slightly thick but pourable.
2. Let the batter rest at room temperature for at least 30 minutes or refrigerate for up to 1-2 days to improve texture and flavor. If chilled, stir gently before cooking as the batter may separate.
3. Heat an 8 to 10-inch non-stick skillet or regular skillet over medium heat. Lightly grease with about 1/2 teaspoon oil or butter before each crepe.
4. Pour approximately 1/4 to 1/3 cup of batter into the center of the pan, then tilt and swirl the skillet to spread the batter thinly and evenly in a circular shape.
5. Cook the crepe for 1 to 2 minutes until the edges are lightly browned and bubbles appear on top. Flip carefully and cook the other side for about 30 seconds to 1 minute until golden. Adjust the heat as needed to prevent burning or rubbery texture.
6. Transfer finished crepes to a plate and stack them, covering with a towel or placing in a warm oven at about 175°F (80°C) to keep warm. Repeat with the remaining batter, greasing the pan between crepes.