300 ml (1/2 pint) boiling water or vegetable stock
2 x 125 g (4 oz) cans mackerel fillets in brine, drained
1/2 red onion, finely sliced
1 small bunch of parsley, roughly chopped
150 g (5 oz) cherry tomatoes, halved
1 small cucumber, deseeded and diced
2 tablespoons lemon juice
16 black olives (optional)
salt and pepper
Place the couscous in a bowl with 1/2 tablespoon of the olive oil, half the harissa and a little salt and pepper. Stir with a fork until well coated. Pour over the measured boiling water or vegetable stock, then cover and set aside for 5–8 minutes, until the grains are tender and the liquid has been absorbed. Uncover, fluff with a fork and tip into a large, shallow bowl to cool.
Meanwhile, flake the mackerel and toss together with the red onion, parsley, cherry tomatoes and cucumber.
Combine the remaining olive oil and harissa with the lemon juice. Season to taste and set aside.
Fold the mackerel salad into the cooled couscous with half of the dressing, and spoon into 4 shallow bowls. Serve scattered with the olives, if using, and drizzled with extra dressing.