Peel and finely chop the onion. Heat the stock. Melt 25 grams of butter in a saucepan. Sauté onion in it. Add rice and after five minutes add 1/4 of the stock and simmer covered over a low heat for 15 to 20 minutes.
Stir from time to time and add the rest of the stock little by little. Cut cheese into small cubes. Fold the cheese cubes, half of the Parmesan cheese and 25 grams of butter into the rice. Serve immediately sprinkled with pepper and parmesan.
Garnish with basil.