Preheat oven to 190°C. Pat dry chicken breasts with paper towel. Heat oil in a frying pan on medium. Cook chicken for 1-2 minutes each side, until browned.
Lay chicken breasts on large individual pieces of baking paper and smear mustard over both sides of each breast. Top with zucchini, tomatoes and herbs. Season to taste.
Wrap chicken loosely in paper, folding ends to prevent juices escaping. Lay parcels on a baking tray and bake for 15 minutes. Place parcels on serving plates and open. Drizzle with extra olive oil and serve chicken with steamed baby potatoes.