In a large mixing bowl, whisk together the all-purpose flour and fine sea salt until evenly combined. Create a well in the center, add two large eggs, and begin incorporating the flour gradually. Slowly pour in whole milk while whisking to achieve a smooth consistency with no lumps. Stir in the melted butter, cover the bowl, and let the batter rest at room temperature for 30 minutes to relax the gluten.

After the batter has rested, preheat a nonstick skillet over medium heat for about 2-3 minutes. Once hot, take a small amount of melted butter and brush a thin layer onto the surface of the skillet to prevent sticking.

Pour approximately 60 ml of the prepared batter into the center of the skillet, quickly swirling it around to coat the base evenly. Allow the crêpe to cook for 1-2 minutes, watching for the edges to lift and the bottom to turn golden brown. Carefully flip the crêpe using a spatula, then cook for an additional 30 seconds until lightly golden on the second side.

Once you have your crêpes ready, take one and spread a thin layer of Dijon mustard on one side, if desired. Add a few slices of cooked ham and a generous sprinkle of freshly grated Gruyère cheese on top. Fold the crêpe into a triangle, encasing the delicious filling within.

Return the filled crêpe to the skillet over low heat. Gently press down with a spatula to help the cheese melt, cooking for 1-2 minutes until the cheese is gooey and the edges of the crêpe are crisp.

Carefully slide the Ham Cheese French Crêpes onto a serving plate. Garnish with freshly chopped parsley and a sprinkle of black pepper for added flavor. Serve them hot.