In a large mixing bowl, whisk together all-purpose flour and a pinch of fine sea salt. Create a well, add eggs, mix and gradually pour in milk until smooth. Stir in melted butter and let rest for 30 minutes.

Preheat a nonstick skillet over medium heat, melt butter to coat the surface.

Pour about 60ml of the batter into the pan, swirl to form a thin layer. Cook for 1-2 minutes, flip and cook for another 30 seconds until golden. Keep warm.

Lay one crêpe flat, spread Dijon mustard if desired, add ham and Gruyère cheese, fold into a triangle.

Cook filled crêpes on medium heat for 1-2 minutes per side until cheese melts and edges are crispy.

Serve warm, garnished with parsley and black pepper.