01 - In a large bowl, whisk together flour and salt. Make a well in the center and add eggs. Gradually whisk in milk and melted butter until smooth and lump-free. Let the batter rest for 10 minutes.
02 - Heat a nonstick crepe pan or skillet over medium heat. Lightly brush with melted butter.
03 - Pour about 1/4 cup batter into the pan, swirling to coat the bottom in a thin, even layer. Cook for 1-2 minutes until edges lift and bottom is lightly golden. Flip and cook another 30 seconds. Transfer to a plate and repeat with remaining batter.
04 - Preheat oven to 350°F (175°C).
05 - Place a few slices of ham (if using), a handful of spinach, and a sprinkle of cheese on each crepe. Add a spoonful of crème fraîche and season with black pepper.
06 - Fold crepes into quarters or roll up. Arrange in a baking dish. Sprinkle any remaining cheese on top.
07 - Bake for 8-10 minutes, until cheese melts and crepes are warmed through.
08 - Serve hot, garnished with extra spinach or a side salad if desired.