Step 2

Heat the remaining oil in a deep pan. Add the fennel, onion and garlic, season, then cover and cook gently for 10 minutes until softened.

Step 3

Meanwhile, parboil the potato chunks for 5 minutes until almost tender. Drain.

Step 4

Add a strip of orange zest, the star anise, bay leaf and ½ tsp harissa to the pan. Fry gently, uncovered, for 5–10 minutes until the vegetables are soft, sweet and golden.

Step 5

Stir in the tomato purée and cook for 2 minutes, then add the chopped tomatoes and prawn stock. Simmer for 10 minutes until the sauce thickens slightly.

Step 6

Add the potato, fish chunks and prawns gently to the stew. Bring back to the boil, then cover and simmer for 3 minutes. Scatter the mussels over the top, cover and cook for 2 minutes more until the shells have opened. Discard any that remain closed.

Step 7

Scatter with thyme leaves. For the rouille, stir the remaining ½ tsp harissa through the mayonnaise. Serve the stew in bowls topped with spoonfuls of rouille and plenty of crusty bread.