30asparagus spears, trimmedTo serve:extra-virgin olive oil100 mlwhite wine vinegar100 mlblood-orange juice, plus finely grated rind of 1 blood orange (see note)½golden shallot, coarsely chopped3egg yolks250 mlwarm clarified butter2 tbspfinely chopped chervil, plus extra sprigs to serve
Blanch asparagus in boiling salted water until bright green (1 minute), refresh, drain and set aside. Just before serving, drizzle with olive oil and season to taste.
Combine vinegar and half the juice in a small saucepan over high heat, add shallot and reduce to 50ml (5-10 minutes). Strain into a large heatproof bowl, add yolks and whisk over a saucepan of simmering water until thick (3-4 minutes). Turn off heat. Whisking continuously, add butter in a thin steady stream until thick and emulsified (3-5 minutes). Stir through remaining juice, rind and chervil and serve warm with asparagus scattered with chervil sprigs.
Note If blood oranges are unavailable,
substitute oranges or ruby grapefruit.