Recipe Method

1. Bring 3 cm salted water to a boil in a large saucepan. Add the asparagus in one layer. Cook until tender, about 5 minutes for medium and 7 minutes for thicker pieces.  Remove from heat and keep warm.
2. For the sauce:  Put a pan of water on to boil and find a glass or heatproof china bowl that will fit neatly into it without actually touching the water.
3. Add the yolks and water. Whisk, pouring in the melted butter, slowly at first as if you were making mayonnaise, then as the sauce thickens up, a little faster.
4. Once it is thick and creamy, squeeze in a little lemon juice and stir in a pinch of salt.