Heat the oil in a 6-quart saucepan over medium heat. Add the chicken, onion, salt, and pepper. Loosely cover the pan to accelerate the cooking.
After 4 to 5 minutes, turn the chicken and add the garlic, rosemary, and thyme. After 2 minutes, add the stock and stir well, scraping the bottom of the pan to release any caramelized bits of chicken or onion. Replace t