Brown the chopped onion with half the butter, stir in the rice and toast it.
Pour the white wine over it, allow to evaporate, and add the previously crumbled marrow. Cover the rice with boiling meat stock and continue cooking. Five minutes before the rice has finished cooking, add the saffron and adjust the seasoning.
When all the liquid has been absorbed by the rice, but when it is still “al dente”, remove from the heat.
Whip with the remaining butter and Parmesan cheese.
To obtain even more flavor, blend in a little veal stock. The rice should be creamy and “swelling”.