Heat the oil in a frying pan and fry the onion, celery and carrots for 4-5 minutes, or until softened. Add the chicken pieces and continue to cook for 2-3 minutes or until the have browned a little.
Pour in the wine and continue to cook until the volume of the liquid has reduced by half. Stir in the tomato purée and the stock.
Add the herbs, reduce the heat and simmer for 30 minutes, or until the chicken is cooked through.
Meanwhile, cook the polenta according to packet instructions. Add the butter and parmesan and stir until well combined.
To serve, spoon the polenta onto serving plates and top with the chicken.