2) Meanwhile, in a large (30-cm) saute pan, heat the cream over medium heat until it comes to a simmer. Add the truffle butter, 1 tsp salt, and 1/2 tsp pepper, lower the heat to very low, and swirl the butter until it melts.
3) Add the drained pasta to the saute pan and toss it with the truffle-cream mixture. As the pasta absorbs the sauce, add as much of the reserved cooking water, as necessary, to keep the pasta very creamy.
4) Serve the pasta in shallow bowls and garnish each serving with a generous sprinkling of chives and shaved Parmesan. Sprinkle with salt and pepper to taste and serve at once.