Heat the oil in the saucepan over medium heat. Cook the thighs until amost browned through.
Meanwhile, chop the onion & rosemary then score the tomatoes at one end (this is so the skins slip off easily).
Remove the chicken to a separate plate. Add the onion to the pan.
Cook the onion for a few minutes without browning it. Then add the rosemary, chilli and salt. Cook a further few minutes.
Add the scored tomatoes to the pan, put the lid on, and continue cooking until a sauce develops and the skins slip off (about 45 minutes). Stir regularly to make sure sure it doesn't catch, and add water intermittently if required.
Add the wine and chicken stock, bring to a boil, then reduce the heat to a simmer.
Return the chicken to the pan, and simmer a further 15 minutes. Stir continually so it doesn't catch, and make sure there is enough sauce with which to cook the risoni.
Add the risoni to the pan, squeeze the lemon over it then mix through.
Put the lid back on and cook a further 3-4minutes until the risoni softens.