Tunisian fish couscous (Couscous au poisson)

1. Cut the fish fillets into 4-8 pieces and salt; chop the onion, crush the garlic, peel the carrots and potatoes and quarter them lengthways.

2. Heat the olive oil in a wide pan and soften the onion for 5 minutes; add the garlic, harissa, cumin and passata and stir for 2 minutes.

3. Pour in the water, season with salt and pepper, add the carrots and potatoes and cook for 20 minutes until the vegetables are almost tender.

4. Carefully lay the fish in the sauce and simmer for 8-10 minutes until cooked through; don't stir, so it doesn't break apart.

5. Meanwhile drizzle the couscous with the olive oil and salted lukewarm water, leave for 10 minutes, fluff it up, then steam it over the sauce or covered for 5 minutes.

6. Pile the couscous in a deep dish, pour some of the red sauce over it so it soaks in, and arrange the fish and vegetables on top.

Tip: In Tunisia, fish couscous is the pride of coastal towns like Sfax and Mahdia; here the couscous turns red from the harissa sauce. Choose firm-fleshed fish (cod, perch, sea bream), as soft fish falls apart.