01 - Whisk together flour and salt in a large bowl. Create a well in the center, crack in the eggs, and gradually incorporate milk and melted butter until smooth. Allow the batter to rest for 10 minutes to relax the gluten.
02 - Heat a nonstick skillet over medium heat and lightly brush with melted butter. Pour approximately 1/4 cup batter into the pan, tilting and swirling to create a thin, even layer. Cook for 1-2 minutes until the edges begin to lift and the bottom turns golden. Flip and cook for an additional 30 seconds. Transfer to a plate and repeat until all batter is used.
03 - Set oven to 350°F for final baking.
04 - Layer ham slices, a handful of spinach, grated cheese, and a dollop of crème fraîche onto each crepe. Season generously with freshly ground black pepper.
05 - Fold each crepe into quarters or roll into cylinders. Arrange seam-side down in a baking dish. Scatter any remaining cheese over the top.
06 - Bake for 8-10 minutes until the cheese is thoroughly melted and the crepes are heated through. Serve immediately while hot.