01 - Whisk flour and salt in a large bowl. Create a well in center, add eggs, then gradually whisk in milk and melted butter until smooth. Rest batter for 10 minutes.
02 - Heat a nonstick skillet over medium heat, lightly brushing with butter. Pour 1/4 cup batter, swirling to coat pan bottom. Cook 1-2 minutes until edges lift and bottom is golden. Flip and cook 30 seconds. Transfer to plate. Repeat with remaining batter.
03 - Preheat oven to 350°F.
04 - Layer ham slices, spinach, and cheese on each crepe. Add a spoonful of crème fraîche and season with black pepper. Fold into quarters or roll up.
05 - Arrange crepes in a baking dish. Sprinkle remaining cheese on top. Bake for 8-10 minutes until cheese melts and crepes are heated through. Serve hot.