For pickled leeks, place ingredients except leeks in a saucepan with 400ml water and 1 tbsp salt flakes; bring to the boil. Reduce heat to low, add leeks and simmer until just tender (3 minutes). Cool completely in pickling liquor.
Step 2
For sauce, combine remaining ingredients except snapper in a bowl, season to taste; set aside until required.
Step 3
Preheat a grill to high heat. Place snapper on large greased oven trays, season and drizzle with oil. Grill on top shelf until skin is crisp and snapper is cooked (20 minutes); rest for 5 minutes.
Step 4
To serve, divide drained pickled leeks among plates and top with snapper. Spoon over orange and pistachio sauce and scatter with extra herbs.