1. Mix the semolina with salted water and oil, so that the grains absorb the liquid without sticking to one another.
2. Steam for about one hour and leave to cool.
3. Drain the vegetable cocktail and aromatize with chopped mint leaves.
4. Add the vegetables and olives to the couscous.
5. Dress with extra virgin olive oil and garnish with the mackerel fillets.