Sounds fairly ordinary, but the unctuous sauce makes it special. An excellent way of stretching a little asparagus to serve a lot of people.
For 6 to 8 people:
Two bunches of asparagus
80 g butter
80 g flour
500 ml milk
200 ml cream
3 egg yolks
40 g freshly grated parmesan
salt and pepper
Preheat the oven to 180C and butter a rectangular gratin dish (the asparagus fits better than it would in an oval one).
Trim and peel the asparagus if necessary and cook it in a large quantity of boiling salted water for about 15 minutes (faffing about with a fancy asparagus steamer is unnecessary). It should be just tender.
Meanwhile, make the sauce: mix the cream and milk and heat to simmering point. Make a roux with the butter and flour, and add the heated milk and cream slowly, stirring constantly. Cook over a low heat until the sauce is smooth and thick. Then remove from the heat, beat in the egg yolks, and season with salt, pepper and nutmeg.
Drain the asparagus, refresh with cold water, and drain very thoroughly. Arrange in the gratin dish, pour over the sauce, sprinkle with parmesan, and bake for 20 minutes until brown and bubbling on top.