extra virgin olive oil • 6 oz. boneless skinless chicken breasts • shredded Parmesan cheese • portobello mushroom caps, gills scraped off with a spoon, thinly sliced • onion, finely chopped • garlic cloves • thin asparagus, ends trimmed and discarded, chopped into 2 inch lengths • shery vinegar or red wine vinegar • chicken stock or broth • cherry tomatoes, whole if small, halved if large. • handful of fresh flat-leaf parsley, chopped