Add 1 tablespoon of salt to a large pot of water and bring it to a boil.
Meanwhile, melt the butter and olive oil in a large (12-inch) saute pan over medium-high heat. Add the mushrooms and saute for 5 to 10 minutes, tossing often, until the mushrooms are cooked and the liquid has evaporated.
Transfer the mushrooms to a bowl and rinse out the pan.
Pour the cream into the saute pan and heat it over medium heat until it simmers. Add the truffle butter, 1 teaspoon salt and 1/2 teaspoon pepper, lower the heat to very low and swirl the butter until it melts. Keep warm over very low heat.
Meanwhile, add the pasta to the boiling water and cook for 1 to 2 minutes. Drain the pasta in a colander and add it to the truffle cream. Add the chives and mushrooms and toss well with tongs. Stir in the Parmesan. Serve hot in shallow bowls, garnished with extra chives and Parmesan.