Bring a large pot of water to a roaring boil. Season with 1 teaspoon kosher salt. Add the fettuccine and cook according to the length of time suggested on the package, to al dente. Stir immediately after adding it to the water and frequently while it is boiling.
1/2 pound fettuccine
In a skillet over medium heat, whisk together the heavy cream and the butter until the butter is melted. Bring it to a simmer, and turn the heat down low. Cook for 15 minutes, stirring occasionally. You should see occasional bubbles.
2 cups heavy cream, 2 tablespoons unsalted butter
Stir in the Parmesan cheese until it melts. Season with salt and pepper, tasting and adding more as needed. We typically add about 3/4 teaspoon salt and almost 1/4 teaspoon black pepper. The seasoning at the end really pulls together the dish, so be sure to play with this.
1 cup Parmesan cheese, 1/4 teaspoon kosher salt, fresh black pepper
Toss with fettuccine and enjoy immediately.