It's not easy to improve upon the famously fabulous combination of walnuts and blue cheese but the addition of yacon, with its succulent sweet crunch, really lightens and freshens this deliciously different lunch. This recipe from Mark Diacono’s A Taste of the Unexpected (Quadrille, £20) serves 4 as a starter.
For the dressing:
Preheat the oven to 180C/Gas 4. Spread the walnuts or pecans out onto a baking tray and toast in the oven for 8–10 minutes, shaking halfway through, until lightly coloured – keep an eye on them to ensure they don't burn. Fill a bowl with water and add the lemon juice. Peel the yacon, cut into slices and toss into the lemony water to prevent them from discolouring. In a small bowl, whisk together the vinegar with the salt before adding the olive oil a little at a time, whisking all the while until smooth. In a bowl, lightly dress the salad leaves in a little of the dressing and divide between 4 plates.
Arrange the sliced yacon on top, crumble over the blue cheese, then trickle over the rest of the dressing. Scatter the nuts over the top and serve immediately.