Here's what you need:
Throw 8-9 ounces of pasta in a pot and cook it up, save 1/2 cup of pasta water for the sauce.
Meanwhile, bring cream and butter to a simmer in a 12-inch heavy skillet over medium-low heat, adding 1/4 teaspoon salt and 1/2 teaspoon pepper.
Add 8-9 ounces of pasta, 1/4 cup reserved water, and cheese to sauce and toss. Add more cooking water if necessary.