Combine the flour, salt, eggs, milk and melted butter in a blender and blend until smooth. Pour into a measuring cup and allow the batter to rest at room temperature for 15 minutes.
Heat a 12-inch nonstick skillet over medium heat. Brush with melted butter. When hot, ladle about 1/3 cup batter into the pan and cook until golden, about 2 minutes. Flip and cook on the reverse side for another 1 to 2 minutes. Remove the crepe from the pan and repeat with the remaining batter.
Fill each crepe with either chocolate-hazelnut spread or cheddar and ham.