In a mixing bowl or blender, combine flour, milk, eggs, melted butter, and salt. Blend until smooth. Let rest for at least 30 minutes.

Heat a non-stick skillet over medium heat. Lightly grease with cooking spray or butter.

Pour approximately 1/4 cup of batter into skillet, tilting to spread into a thin layer. Cook for 1-2 minutes, then flip and cook until golden.

Stack cooked crepes on a plate and keep warm.

In a separate pan, scramble eggs until soft. Add spinach, cheese, tomatoes, and chives, mixing until cheese melts and heated through.

Spoon filling onto center of each crepe, fold sides, and roll up. Serve warm with sour cream or hot sauce if desired.