Place the chicken breasts between two sheets of cling film and beat with the flat side of a meat mallet or rolling pin to flatten slightly. Season well.
Place the lime juice and zest, oil, chilli and coriander in a shallow dish and whisk together with a fork. Add the chicken, turn each piece so that it is coated in the marinade. Cover, chill and allow to marinate for at least 1 hour.
To make the cauliflower couscous
Place the cauliflower florets in a food processor and using the pulse button, blitz in short bursts until the cauliflower has the texture of couscous.
Heat the oil in a large frying pan and tip in the cauliflower. Stir-fry for about 5 minutes until it is beginning to turn golden in colour.
Add the water and season well. Cover with a lid and cook for about 5 minutes until the cauliflower is tender and the water has evaporated. Keep warm.
Meanwhile, remove the chicken from the marinade. Cook under a hot grill or on a griddle pan for 3 to 4 minutes each side until cooked through (juices will run clear).
Stir the lime juice and zest into the cauliflower couscous along with the chopped coriander and serve with the chicken.