For the piri-piri prawns, place all the ingredients except the prawns into a food processor and blend until smooth.
Place the prawns on a plate and rub over the piri-piri sauce, reserving a little to garnish. Leave to marinate in the fridge for an hour.
Heat a griddle pan until hot and cook the prawns for 4-5 minutes on each side, depending on their size, until the prawns have turned pink and are cooked through.
For the couscous, place the couscous into a bowl, pour over the boiling water and stir with a fork to combine. Add the harissa, pomegranate molasses, baharat and lemon juice and stir once more. Cover with cling film and set aside for 3-4 minutes, until all the liquid has been absorbed into the couscous.
Remove the cling film and fluff up with a fork. Add the red onion, fleshy pomegranate seeds and coriander and mix well.
To serve, place three prawns onto each plate with a pile of couscous. Drizzle over the reserved piri-piri sauce and a squeeze of lemon.