In a heavy based sauce pan, sweat Onion, Garlic & Mushrooms in a little olive oil. Add Rice & sweat till almost transparent. Add White Wine & reduce till liquid is almost gone, before gradually adding more stock, small amounts at a time, stirring constantly between each addition.
When Rice is cooked and al dente, has a slight crunch to it, remove from heat, add lemon juice, cold diced butter, parmesan & thyme and correct seasoning, add a splash of white truffle oil if desired. Set in roasting tray and cool. Roll into bite sized balls and coat with fine polenta, deep fry or brown in fry pan with little olive oil.