Heat half the oil in a large, deep frying pan. Fry the chicken over a high heat for 6 minutes, turning once. Lift chicken out; set aside on a plate.
Heat the remaining oil in the pan and fry the onion and mushrooms over a medium heat for 8 minutes or until beginning to soften. Stir in the tomatoes, origanum, bay leaf and chicken stock or water. Return the chicken to the pan, bring the mixture to the boil and simmer for 15 minutes, turning the chicken halfway through the cooking time, until the chicken is cooked through and the sauce has thickened.
Remove the bay leaf, then season well and stir through the rocket. Serve with seasonal vegetables or crusty bread to mop up the juices.
Each serving 1 143kJ, 7g fat (2g saturated), 9g carbohydrate (8g total sugars).