Heat the olive oil in a wok over a medium heat, add the leek, onion, garlic, chilli, preserved lemon, cumin and fennel seeds with a big pinch of salt and cook until the leek and onion are softened and fragrant – about 10 mins. Add the Silver Beet, herbs and a good squeeze of lemon juice and season, cook for a few mins until the leaves are wilted but not mushy. Allow to cool, and then squeeze the Silver Beet in a sieve to remove any excess moisture.