Asparagus, fennel and beetroot with verjus

Verjus, or verjuice, is a sour juice made from unripe grapes. It was very popular in medieval times and is still used for making sauces in a few traditional French dishes. I was reminded of it by Ramael Scully, the former evening chef of Ottolenghi in Islington. Scully trained as a chef in Australia, where verjus has been regaining popularity in recent years as an alternative to vinegar in sauces and dressings