- Cook potatoes in a large saucepan of salted boiling water until tender (10-20 minutes). Drain, then set aside to cool slightly.
- Meanwhile, combine crème fraîche, lemon juice and rind in a small bowl, season to taste.
- Combine potatoes (halve larger ones) in a large bowl with crème fraîche mixture, onion and half the dill, watercress and purslane, season to taste and toss to combine. Arrange remaining greens and capers on a platter, top with potato mixture and serve.
Note: Tuscan red onion is a long oval-shaped red onion. If it’s unavailable, substitute half a Spanish onion. Purslane is available from select greengrocers. If it’s unavailable, use extra watercress.
The key is to use really fresh potatoes from a good greengrocer. Chat potatoes work well because they are creamy and small, but if you want to use a larger potato, the royal blue variety also has a lovely creamy texture. Purslane, a succulent used in Greek and Italian cooking, adds a delicious tang here.