In a medium saucepan heat the stock until boiling. Add the dried mushrooms and cover. Leave to simmer for 20 minutes and then remove the mushrooms and strain back into the pot.
Chop the mushrooms and set aside. Meanwhile, keep the stock hot.
In a large sauce pot heat the olive oil over high heat. Add the onions and cook until     translucent, about 5 minutes.
Add the garlic and the rice. Cook until the rice becomes slightly translucent or shiny and begins to smell nutty, almost like popcorn, about 8 minutes.
Now slowly add the stock until it reaches just to the top of the rice. Continue to cook over medium-high heat stirring often. The goal is to reduce the stock and agitate the rice.
Once most of the stock has reduced continue raising the level just to the top of the rice. This should take 5 or 6 additions of stock, or until all the stock is used up, about 40 minutes total.
Meanwhile, in a large frying pan cook the sliced mushrooms over high heat just until they are soft. Add them to the risotto and de-glaze the pan with the white wine.
Lastly add the white wine and let cook until the wine has cooked out.
Add the butter and Parmesan and stir the rice vigorously until it becomes thick and shiny, about 3 minutes.
Add chopped chives to garnish and serve
Ingredients
1/4 cup olive oil
1 onion, chopped
2 cloves garlic, minced
2 litres vegetable or chicken stock
2 1/2-ounce packages dried porcini or shiitake mushrooms