2 leeks, pale part only, sliced into half moons
½ fennel bulb, thinly sliced
1 bay leaf
40g (heaped ¼ cup) plain flour
150ml dry white wine, such as sauvignon blanc
200ml fish stock
Salt flakes and freshly ground black pepper
2 large handfuls of roughly chopped flat-leaf parsley
2 tsp roughly chopped dill fronds
2 tsp roughly chopped tarragon leaves
250g smoked cod or trout fillet, skin and bones removed, cut into 4cm cubes (optional)
700g snapper fillet (or similar firm white fish), skin removed, cut into 4cm cubes
6 raw king prawns, shelled and deveined, chopped into 3 pieces
130g (1 cup) frozen baby peas
2 tbsp finely grated parmesan
Olive oil, for drizzling
Mashed Potato Crust
1.5kg desiree potatoes (about 4 large), cut into 5cm chunks
100g butter, diced
Pinch of freshly grated nutmeg
Melt the butter in a large saucepan over low heat, add the leek, fennel and bay leaf and fry, stirring occasionally, for 20 minutes until the leek is very soft and has started to caramelise.
Add the flour and stir for 5 minutes until sandy coloured. Gradually pour in the wine, stirring well between additions, then add the stock in the same way. Increase the heat to high and bring to the boil, stirring for 1 minute until combined and thickened. Season with salt and pepper and stir in the herbs. Remove from the heat, pour into a 2L baking dish, cover and set aside.
For the potato crust, place the potato in a saucepan of cold, salted water and bring to the boil. Cook for 12–15 minutes until tender. Drain well, return to the pan and add the cream. Place over medium heat and bring the cream to the boil. Remove from the heat and mash the cream and potato with a potato masher until smooth. Add the butter, a piece at a time, stirring well to combine. Season and add the nutmeg.
Preheat the oven to 200°C.
Scatter the fish, prawns, peas and parmesan over the sauce in the dish, then spread the mashed potato over the top to cover. Drizzle lightly with the olive oil, then bake, turning the dish occasionally, for 50–55 minutes until the filling is bubbling and the crust is golden. Serve hot accompanied by a green salad.