Cook potatoes in boiling salted water for 20 minutes, or until just cooked. Rinse under cold running water. Peel and dice when cool enough to handle. Place potatoes, rocket, onions, tomatoes and olives in a serving bowl.
To make caperberry vinaigrette, whisk vinegar, 1 to 2 tablespoons caperberry brine, mustard and oil until combined. Add salt and pepper to taste. Pour vinaigrette over salad and toss gently to combine.
Leave salad, covered, in a cool place 30 minutes. Add more salt, pepper and vinegar to taste. Slice caperberries in half and add to salad.
If the potato salad becomes a little dry while standing, add 2 tablespoons or so of hot stock (broth). Let stand 5 minutes before serving.
Caperberries are the fruit of the caper bush. They are about 2 cm (1 inch) long and are pickled in brine with their stems intact. They are available from delicatessens and some supermarkets. Eat whole as part of an antipasto plate. Alternatively, slice for use as a garnish.
light potato salad with baby spinach
Cook and peel 800 g (1 lb 12 oz) potatoes as described in the main recipe; cut into rounds instead of dice. * Finely slice 3 spring onions (scallions). Tear 150 g (5 oz) baby spinach leaves into small pieces. Place salad in a bowl. Whisk 1⁄2 cup (125 g/4 oz) low-fat yogurt, 1⁄2 cup (125 g/4 oz) light sour cream, 1 tablespoon white wine vinegar, 1 tablespoon lemon juice and 2 tablespoons olive oil until combined. Pour over and toss through salad. Add salt and pepper to taste.