Step 1

For the broth, combine all ingredients, except tomato paste and oil, in a bowl with the reserved fish bones. Cover and place in the fridge to marinate overnight.

Step 2

The next day, strain the broth mixture, reserving the fish bones and spices. Heat the oil in a large saucepan over high heat. Add the strained bones and spices

Step 3

Cook, stirring constantly, for 2 minutes, then add tomato paste, and cook, stirring, for a further 2 minutes or until coated. Deglaze pan with reserved liquid, scraping bottom of the pan with a spoon. Cook for a further 2 minutes or until slightly reduced.

Step 4

Add 3L (12 cups) water and bring to a simmer. Reduce heat to low. Cook for 20 minutes or until slightly reduced. Strain through a fine sieve. Discard solids. Set aside.

Step 5

Heat 1/4 cup (60ml) oil and 25g butter in a large pan over medium heat until the butter is foaming. Add onion, garlic and pancetta, and cook, stirring, for 2 minutes or until onion has softened. Add carrot, celery and celeriac, and cook, stirring to coat all the vegetables, for 10-15 minutes until softened. Add parmesan rind, if using, tomato passata, bay leaf and 2L (4 cups) reserved broth.

Step 6

Cover and simmer gently for 15 minutes. Add cavolo nero, zucchini and green beans, and cook for 5 minutes or until zucchini is tender. Season to taste. Remove and discard cheese rind. Stir through parsley, borlotti beans and lemon juice. Remove from heat. Keep warm.

Step 7

Melt the remaining 25g butter in a frypan over medium heat. Cook fish, turning halfway, for 5 minutes or until cooked through. Serve minestrone with flaked fish.