In a blender, combine the flour, eggs, milk, water, 3 tbsp melted butter, and salt. Blend on high speed for 20-30 seconds until completely smooth and frothy. Let the batter rest at room temperature for at least 10 minutes (or up to 1 hour) to allow the gluten to relax, which results in more tender crepes.

Heat an 8-inch non-stick skillet or crepe pan over medium heat. Lightly brush the pan with melted butter. Pour about 1/4 cup of batter into the center of the pan, immediately tilting and swirling the pan to spread the batter into a thin, even circle. Cook for 1-2 minutes until the edges look dry and the bottom is lightly golden brown. Use a thin spatula to carefully flip the crepe. Cook for another 30-45 seconds on the second side. Transfer to a plate. Repeat with the remaining batter, stacking the cooked crepes with parchment paper in between to prevent sticking. You should get 8-10 crepes.

While the crepes cook, prepare your hollandaise sauce using your preferred method (see Pro Tips for a blender version). Keep the sauce warm in a thermos or a bowl set over (not in) a pot of warm water. Lay the ham slices flat and, if they are large, you can fold or tear them to fit neatly inside the crepes.

Lay a crepe flat on a work surface. Place one slice of ham (or a portion of slices) in the center, slightly off to one side. Gently roll the crepe into a tight cylinder. Place the rolled crepe seam-side down on a serving plate. Repeat with the remaining crepes and ham.

Arrange 2-3 rolled crepes per serving plate. Generously spoon the warm hollandaise sauce over the center of the crepes, allowing it to drizzle down the sides. Garnish with a sprinkle of fresh chopped parsley. Serve immediately.