For one pound of pasta.

1 cup heavy cream
2 cups Parmesan cheese
1/2 cup (1 stick) unsalted butter, softened
Nutmeg

In large heavy pan place 2/3 cups of the cream and all the butter. Simmer over low heat until butter and cream have thickened slightly (about 1 minute). Remove from heat, and add 1 pound of cooked and drained pasta of your choice. Return to heat. Toss to coat well. Add remaining cream, cheese and nutmeg. Toss again. Add salt and freshly ground pepper to taste.