Heat the oven to 200C/180C fan/gas 6. Mix the butter with the remaining garlic, lemon zest, remaining cumin and a small pinch of salt. Loosen the skin of the chicken breast using your hands, carefully, so as not to tear the skin. Work from the widest part of the bird and get close to the neck but not all the way through, and try to loosen the skin above the legs as well. Gently push the garlic butter under the skin as far as it will go. Stuff the cavity with the rice mixture, then tie the legs together to stop it from spilling out.