Heat half the butter in a large saucepan and fry the chicken for 6-8 minutes until browned and fully cooked through. Remove from the pan and set aside.
Add the remaining butter to the pan and cook the onion for 5 minutes until soft. Stir in the rice and cook for a further minute.
Gradually add the stock, a ladle at a time, stirring frequently, adding more as the liquid is absorbed. Cook slowly over a low heat for about 15 minutes until nearly all the stock has been absorbed. Add the chicken, ham, broccoli and peas, and cook for a further 5 minutes.
Stir through the soft cheese. Scatter over the grated cheese and grind on freshly ground black pepper and serve.