Asparagus spears with wholegrain mustard hollandaise

1. Put the yolks and 2 tsp lemon juice in a small blender or food processor; whizz for 30 seconds. Melt the butter in a small pan then, with the blender running, trickle it in.

2. Warm a bowl by pouring a little just-boiled water into it, then empty and dry. Scrape the hollandaise into the bowl and stir in the mustard; season with salt, pepper and more lemon juice to taste. Leave in a warm (not hot) place for up to 30 minutes.

3. Lay the asparagus out in a single layer in a large frying pan. Half-cover with just-boiled water, add a pinch of salt and place over a high heat. Simmer briskly, turning the spears occasionally, until the water has evaporated and the asparagus is tender. Serve with the warm sauce and lemon wedges, if liked.