Fish with green sauce and white bean purée

Ingredients

• Green sauce
• 1/2 cup finely chopped fresh flat-leaf parsley
• 1/4 cup each finely chopped fresh mint, dill and chives
• 1 tablespoon wholegrain mustard
• 2 tablespoons lemon juice
• 2 tablespoons rinsed, drained baby capers, chopped finely
• 1 clove garlic, crushed
• 1/4 cup (60ml) olive oil
• 1 tablespoon olive oil
• 1 medium brown onion(150g), chopped finely
• 1.2 kilograms (2½ pounds) canned white beans, rinsed, drained
• 1 cup (250ml) chicken stock
• 1/4 cup (60ml) pouring cream
• 4 x 200g (6½-ounce) whitefish fillets, skin-on