01 - Whisk together flour and salt in a large bowl. Create a well in the center and crack in the eggs. Gradually whisk in milk and melted butter until smooth and lump-free. Let batter rest for 10 minutes to allow gluten to relax.
02 - Place a nonstick crepe pan or skillet over medium heat. Lightly brush the surface with melted butter to prevent sticking.
03 - Pour approximately 1/4 cup batter into the heated pan, immediately tilting and swirling to coat the bottom in a thin, even layer. Cook for 1-2 minutes until edges begin to lift and the bottom appears lightly golden. Flip carefully and cook for an additional 30 seconds. Transfer to a plate and repeat with remaining batter, stacking crepes as they finish.
04 - Preheat oven to 350°F.
05 - Layer a few slices of ham, a handful of spinach, and a sprinkle of grated cheese on each crepe. Add a spoonful of crème fraîche and season with freshly ground black pepper to taste.
06 - Fold each crepe into quarters or roll into cylinders. Arrange the filled crepes in a single layer within a baking dish. Sprinkle any remaining cheese over the top.
07 - Bake for 8-10 minutes, or until the cheese has completely melted and the crepes are heated through.
08 - Serve immediately while hot, optionally garnished with fresh spinach leaves or accompanied by a crisp side salad.