Heat 2 tablespoons of the butter with the olive oil in a large deep sided pan over a medium-low heat. Add the fresh mushrooms and cook for about 2 minutes.
Add the shallot and the garlic and cook for another two minutes.
Season lightly with salt and pepper.
In another medium sized saucepan, bring the chicken broth to a boil. Reduce to a simmer.
Stir the rice into the mushroom mixture and let the oils coat the grains. Continue toasting the rice, stirring constantly, for about 3 minutes.
Add the Champagne and simmer until the liquid has almost evaporated, about 3 minutes.
Add 1 cup of the simmering broth and stir until almost completely absorbed, about 2 minutes.
Continue cooking the rice, adding the broth 1 cup at a time, stirring constantly and allowing each addition of the broth to absorb before adding the next, until the rice is tender and the mixture is creamy, about 30 minutes. (You many not need to add the additional cup of broth)
Remove from the heat.
Add the remaining butter, parmesan cheese and salt to taste.