Prepare the polenta sticks in advance: Preheat the grill to high. Place the capsicum halves on the grill tray, cut-side down, and grill for 10 minutes or until the skin is charred all over. To make them easy to peel, transfer them to a polythene or paper bag and leave to stand for 15 minutes or until cool enough to handle. Peel the capsicums and cut the flesh lengthways into 5 mm wide strips. Set aside.
Cook the polenta with the salt according to the instructions on the packet. Continue to cook, stirring constantly, until it is thick.
Sprinkle a plastic chopping board or tray with water and turn the polenta out onto it. Use a wet palette knife to spread out the polenta into a rectangle about 1 cm thick. Arrange the strips of capsicum diagonally on top, gently pressing them into the polenta. Wet a sharp knife and use this to trim and neaten the edges of the polenta rectangle. Leave to cool.
Preheat the oven to 200ºC and grease a baking tray. Sprinkle the Parmesan over the polenta and cut it into 16 sticks. Transfer the polenta sticks to the baking tray and bake for 15 minutes or until the cheese is melted and bubbling. Leave to cool for 2 minutes, then transfer to a wire rack and leave to cool completely.
To make the soup: Pour the stock into a saucepan. Tie the bay leaf, parsley and thyme together into a bouquet garni and add to the pan with the celery, fennel, carrots, lemon zest, shallot, garlic and chilli, if using. Heat gently until boiling, then leave to simmer for 5 minutes or until the vegetables are slightly tender. Cover the pan and remove it from the heat. Leave to stand for 10–20 minutes so the flavours can infuse the liquid.
Remove and discard the bouquet garni and chilli halves. Bring the liquid back to the boil. Reduce the heat, add the fish and poach for about 4 minutes or until all the fish pieces are opaque and will flake easily. Season with salt and pepper to taste.
Transfer the polenta sticks to a serving plate. Ladle the soup into warmed bowls and sprinkle with the fennel leaves. Serve at once.
Some more ideas…
When you're in a hurry, serve the soup with cornbread instead of the polenta sticks.
• If don't make your own low-salt stock, try a high-quality commercial stock rather than a stock cube to keep the added salt to the minimum. • Celery and fennel provide potassium. Celery also acts as a diuretic, helping to reduce fluid and salt retention. • White fish is very low in fat and kilojoules.