Put the oil in a large frying pan over a medium heat. Add the garlic and fry until crisp. Scoop the garlic out of the pan and set aside on kitchen paper to drain. Leave the remaining oil in the pan.
Stir the Cajun spice into the oil, then add the prawns. Fry for 4 minutes, or until the prawns are cooked through, tossing regularly. Add the agave syrup and heat for 30 seconds. Season with salt and a squeeze of lime juice.
Mix the couscous or fregola with the herbs and olive oil. Season well.
5. To serve, divide the couscous between 2 plates, then top with the prawns and crispy garlic.