Warm the chicken stock in a large enough saucepan over medium low heat. Keep at a very warm/hot temperature below boiling.
Heat a large, deep skillet or pan over medium heat and then add olive oil.
Add onion and reduce heat to medium low. Sauté until onion is translucent without browning the onion.
Add the first 1 Tbs butter until melted and increase heat to medium
Add rice to skillet and coat the grains of rice with the butter. Saute for a minute or so
Add the wine and cook until pan is starting to dry out and wine is absorbed. Stir often with a rubber spatula or wooden spoon so rice doesn't stick to the pan.
Once wine is absorbed, start adding the hot stock from the saucepan to the rice one ladle at a time (about ½ cup). Stir often.
Continue adding stock as it gets absorbed by the rice a ladle at a time. Continue stirring throughout this process.
After about ⅔ of the stock has been added and absorbed, taste the rice - you want the texture to be firm but done - not mushy.
You may not need all of the stock. If you need more stock and run out, you can use hot water to add to the rice.
Once the rice is done, remove from heat and stir in remaining butter, salt and pepper and parmesan.
Cover with a lid and set aside as you make the mushrooms.