1.Bring saucepan of salted water to boil. Add potatoes, cover and cook for 15 minutes or until just tender.
2.Meanwhile, whiz herbs, garlic, lemon juice, capers and mustard in food processor until roughly chopped, while pouring extra-virgin oil down spout. Transfer to bowl.
3.Drain potatoes and, while still warm, add to salsa verde and season with salt and pepper.
4.Heat olive oil in pan on high. Dust fish skin with cornflour and shake to discord excess. Cook in pan skin-side down for 4-5 minutes. Turn and cook for 3-4 minutes or until cooked through.
5.Arrange warm salsa verde potatoes on plate and place fish on top to serve.