Start by assembling all ingredients so they’re ready to go.

Bring a large pot of water to a rolling boil and add a generous pinch of salt. Drop in the spaghetti and cook, stirring occasionally, until al dente—tender yet firm to the bite—this typically takes about 10 to 12 minutes. Once done, drain the pasta and transfer it to a large serving bowl.

While the spaghetti cooks, prepare the garlic oil. In a cold skillet, combine the olive oil and sliced garlic. Set the pan over medium heat and allow the garlic to slowly toast. As the oil begins to shimmer and bubble gently, reduce the heat to medium-low. Continue cooking, stirring frequently, until the garlic turns a warm golden hue—this should take around 15 minutes total. Remove the skillet from the heat immediately to prevent burning.

Season the drained pasta with red pepper flakes, a pinch of salt, and freshly cracked black pepper. Pour the fragrant garlic-infused oil over the spaghetti and toss well. Sprinkle in the chopped parsley and half of the Parmigiano-Reggiano, tossing everything until evenly coated.

Serve immediately, topped with the remaining cheese for a final touch of richness and depth.