Let the finely chopped onion in the melted butter become translucent. Fry the rice for 5 minutes while stirring, pour in the hot chicken stock and pour in the peas without defrosting. Season with salt and pepper and cook on a low heat for 20 minutes. Then fluff with a fork and fold in both types of cheese. Tip: Add 200 g of ham, cut into small pieces, to make the dish the main meal.