Bring a large pot of heavily salted water to a boil. Add the spaghetti and cook according to the package instructions until al dente.

Before draining the pasta, carefully scoop out and reserve at least 1/2 cup of the starchy pasta water. Drain the spaghetti and set aside.

In a large skillet, melt the unsalted butter over medium-low heat. Add the minced garlic and sauté for 1 to 2 minutes until fragrant, being careful not to let it brown.

Add the drained pasta directly to the skillet with the garlic butter. Pour in 1/4 cup of the reserved pasta water and toss continuously until a silky sauce begins to form.

Remove the skillet from the heat. Gradually sprinkle in the freshly grated Parmesan cheese and chopped parsley, tossing vigorously. Add more pasta water a tablespoon at a time if the sauce needs to be thinned.

Season with black pepper and additional salt if needed. Serve immediately.