For the spice mix, place the garlic, lemon zest and juice, paprika, ground coriander and cumin in a small bowl and combine. Remove 1½ tablespoons of this mix and set aside (for the dip).
Add the oil to the remaining spice mix in the bowl, season and stir together to make the chicken marinade. Place the chicken in a dish, pour over this mix and leave to marinate for at least 30 minutes.
Meanwhile, heat the barbecue until the coals are grey, or preheat the grill to medium-high. Grill the chicken for 15-20 minutes, turning frequently, until cooked through.
While the chicken is cooking, mix the chopped fresh coriander and reserved spice mix into the crème fraîche for the dip. Serve with the chicken and salad.