Preheat the oven to 180C/350F/Gas 4 and preheat the grill to high.
For the pancake batter, place the eggs into a mixing bowl and whisk in the flour. Add the salt and half of the milk. Finally, whisk in the butter and remaining milk to achieve a thin, pouring cream consistency. Chill in the fridge for 30 minutes.
Melt a small knob of butter in a 20cm/8in non-stick frying pan. Once it is hot and sizzling pour in enough batter to thinly cover the base of the pan. After 30 seconds you can lift the edge with a palette knife to see if it's tinged gold as it should be. Flip the pancake over, cook the other side for a few seconds, and then slide it out of the pan onto a plate.
Without greasing the pan again, repeat the process in stage three to make eight thin pancakes.
For the hollandaise sauce, whisk together the egg yolks with a tablespoon of water in a stainless steel saucepan set over a very low heat, until thick and smooth.
Remove the pan from the heat and continue to whisk while adding the melted butter in a thin stream, leaving behind the milky residue that has settled in the bottom of the butter pan. Season the sauce with salt and freshly ground black peper and sharpen with lemon juice, to taste. Keep warm.
Boil the asparagus in salted water until tender. Once cooked, refresh the asparagus in a bowl of iced water. Drain and pat dry.
To assemble the délices, place a slice of ham on top of a pancake, then arrange three asparagus spears upon it. Roll up and place into a lightly buttered baking dish. Repeat with the remaining pancakes, parma ham and asparagus. Bake in the oven for about 20 minutes, or until just beginning to crisp at the edges.
Serve the délices on a serving dish and coat each one carefully with a spoonful of hollandaise sauce, running it along their length. Very briefly flash the délices under the grill until only just gilded by the heat.