In a large saucepan of suitable size, slowly grill the onion and leek, with about 5 tablespoons of olive oil for 5 minutes until they are soft and tender. With a small spoon, remove and discard the soft and tasteless core of the zucchinis and chop the rest in the pan. Chop the potatoes into coarse 2 cm/1 inch pieces and add to the saucepan. Mix everything well and add the anchovies. Reduce heat and add the white wine. Cook until reduced by half before adding the milk and broth. Bring to a boil and simmer for half an hour until the potatoes are tender. At this stage, add the cod and simmer for another 15 minutes until the flesh flakes apart. Don’t hesitate to stir and break the fish, but it’s good to leave some large pieces as well. Season carefully to taste. Divide among bowls and serve with a small handful of parsley and chives, with a little oil and lemon juice.

Alternative: Sprinkle a little orange zest over the parsley and chives. It’s delicious with cod.