1.Preheat oven to 220°C.
2.Combine parsley, oil, vinegar, capers, anchovy paste and garlic in a small bowl. Season with pepper, to taste. (Makes 1/2 cup.)
3.Pat fish dry and season with salt and pepper. Cut 4 pieces of baking paper (about 30 x 40cm) and spray with olive oil to coat. Arrange one-quarter of the potatoes in the centre of each.
4.Top each with 1 fish fillet and one-quarter of the onion. Fold up the paper tightly to make a parcel and put on a baking tray.
5.Bake parcels until the fish is cooked through and potatoes are tender, about 15 minutes. Allow to stand for 5 minutes. Transfer bags to serving plates, cut open the tops and serve with salsa verde and lemon wedges.
Nutritional info per serving
1,550 kJ (371 cal), 37g protein, 13g carbs, 2g fibre, 18.5g fat (2.5g sat fat), 369mg sodium