Saute one finely chopped medium onion and the mushrooms in butter and oil until soft.
Add the risotto rice and coat until translucent.
Add the bottle of beer and cook until evaporated..
Add the stock to the rice, one ladel at a time, and simmer while continuously stirring.
After about 15 minutes, the stock will have been absorbed, the rice will be cooked to a creamy consistency and still have an al dente bite in the middle.
For a less al dente consistency, add a ladleful of the stock and simmer until absorbed.
Continue until the rice reached the desired consistency.
Stir in the grated parmesan and serve with a drizzle of olive oil.