In 2002 the literary agent Felicity Rubinstein found herself drawn to a white-walled deli that had just opened around the corner from her home in London’s Notting Hill. It was called Ottolenghi and its food display was a riot of colour and promise. Eating it looked like it might be a quick route to feeling good about yourself. “I became rather obsessed with it,” she says now. “I reckoned it wasn’t difficult to make this food. I just had to know...