Heat 1 tablespoon of the olive oil in a large pan and fry the chicken pieces and sliced chorizo until golden, then remove and set aside.
Heat the remaining tablespoon of oil in the pan, add the chopped onion and cook for 5 minutes until starting to soften.
Add in the chopped courgettes and mushrooms, and fry until they begin to turn golden, then add the crushed garlic and cook for a further 1 minute.
Stir in the mixed olives, chopped tomatoes, and return the chicken and chorizo to the pan. Add the chicken stock and bring to a simmer.
Cover and cook for 40 minutes, or until the chicken is tender, then serve with flat leaf parsley or basil leaves scattered on top.