Preheat the oven to 190°C.
Using sharp kitchen scissors, cut the chicken along the backbone. (Remove the backbone, if preferred). Flatten the chicken by placing it skin-side up on a cutting board and pushing down the breastbone.
Cut the lemons and one onion into 1 cm thick rings. Line the middle of a large roasting tray with these, then put the chicken on top, breast facing upwards.
Mix the glaze.
Using a silicon brush, glaze the chicken with half of the mixture, then roast in the oven for 15 minutes. Set the remaining glaze aside.
Meanwhile, tear the cauliflower into small florets. Cut the onion into thin wedges. Drain the chickpeas.
Take the chicken out of the oven, and turn the oven temperature down to 170°C.
Scatter the cauliflower, garlic and onion around the chicken, then brush them with the remaining glaze. Pour in the wine or stock and bake for 25 minutes.
Scatter the chickpeas over the veggies, then mix well. Baste the chicken and cauliflower pieces with the jus.
Roast for another 5-10 minutes or until the chicken skin looks golden and the meat has cooked through (the juices should run clear when pierced with a knife at the legs). Also, the cauliflower should be tender (not mushy!)
Transfer the chicken to a plate and rest for 5 minutes before carving.
Serve the chicken with the cauliflower, onion and chickpeas, together with the cooking juices.