Heat your oven to 180°C (probably a bit more if not fan-assisted).
Take the fat off the top of the leftover gravy, add a dash of olive oil and fry a chopped onion in it for a few minutes until soft. Add some of the leftover chicken meat, in reasonably small pieces, and fry for a few minutes more. Add 200g of arborio rice and keep frying for another minute or two.
Meanwhile, put the rest of the leftover gravy in a measuring jug, add a splash of white or rose wine and top up to 470ml with chicken stock (no stock cubes, please). When you've finished frying the rice, add the stock to the pan and bring it to a simmer. While it's heating up add some halved black olives and some frozen petits pois (or whatever other vegetable you feel like), and season.
When it comes to the simmer, put it in the oven for 18 minutes. Then serve it with grated parmesan (we often omit the parmesan with risotto, but this one really benefits from it).