Add 4 cups of water to a large pot or high-sided skillet, and sprinkle in the kosher salt. Bring the water to a rapid boil. Once boiling, add the bucatini or spaghetti and cook for two minutes less than the package instructions direct. This will ensure the noodles are firm and chewy, which is what we want for this dish.
While the pasta is cooking, heat another large sauté pan over medium heat. Pour in the olive oil, followed by the butter and freshly ground black pepper. Stir gently until the butter melts completely and the pepper releases its delightful aroma.
When the pasta is about 2 to 3 minutes away from being done cooking, carefully measure out and set aside ½ cup of the pasta water. Gradually add this to the olive oil and pepper mixture in the sauté pan. Be cautious; it will bubble and splatter, creating a beautiful sauce. Then, add another ½ cup of the pasta water, mixing well.
Use tongs to transfer the pasta directly from the pot to the sauté pan, allowing some of the pasta water to follow. You don't need to completely drain off the water; it's crucial as it helps create that creamy sauce. Continue cooking the pasta in this oil and pasta water combo for an additional 1 to 2 minutes.
As you cook, toss and stir the pasta to ensure each strand is coated in the rich sauce. If it looks too dry, don’t hesitate to add more of the reserved pasta water, stirring to achieve a thicker sauce that clings to your noodles.
Once the pasta is cooked al dente, remove the pan from the heat. Sprinkle in half of the Parmesan cheese and toss quickly; remember not to stir vigorously! You want that cheese to melt and incorporate into the sauce without clumping.
As the cheese melts, continue to add pasta water as needed to create a creamy texture. The sauce should be smooth and lightly coat each noodle, making it utterly delicious.
Once you're satisfied with the creaminess, taste the dish and adjust the seasoning by adding more freshly ground black pepper if desired. Garnish with chopped parsley for a splash of color.
Serve your Cacio e Pepe hot, and enjoy every cheesy bite!