Preheat the oven to 175°C.
Mix the butter with the cumin, coriander, paprika, cayenne and cinnamon, salt & pepper. Rub half of the spice butter under the skin and over the chicken, including the cavity. Put the lemon halves into the cavity.
Place the chicken in a large roasting tray.
Cut the onion into quarters; the aubergine and carrot into large chunks. Rub them with the remaining spiced butter then scatter them around the chicken, together with the garlic cloves.
Put the chicken in the oven, on the lower shelf. Bake for 30 minutes.
Meanwhile mix the chicken stock with the paste.
Turn over the chicken, letting out the juices from the cavity into the tray. Pour over half of the stock mixture. Cook for another 30 minutes.
Take the chicken out of the oven, transfer to plate. Add the chickpeas and the remaining spiced stock to the tray, mix well with the other vegetables, turning them over.
Place the chicken back into middle of the tray (again, tilt it a bit to allow the lemon juice to escape from the cavity).
Bake for another 35 minutes or so, until clear juices are coming out of the legs (check by inserting a knife to the inner thighs!)
When the chicken is cooked through, transfer it to a serving plate and rest for 10 minutes (covered).
Carve and serve with the chickpeas & vegetable sauce, scattered with fresh chopped herbs on top.