Bring a large pot of salted water to a boil. Add the spaghetti and cook according to the package instructions until al dente. Reserve about a cup of pasta cooking water before draining the pasta.
While the pasta is cooking, heat the olive oil in a large skillet over medium heat. Add the garlic slices and crushed red pepper flakes. Cook for 1-2 minutes, stirring frequently, until the garlic is golden brown but not burnt. Adjust the heat if needed to prevent burning, or take off the heat, until the pasta is done cooking.
Once the pasta is cooked, use tongs to transfer it directly from the pot to the skillet with the red pepper garlicky oil. Toss the pasta in the garlic and oil mixture, ensuring each strand is coated evenly. Add the reserved pasta water, a little at a time, until you achieve your desired sauce consistency- I find ½ cup is perfect. Toss over low heat for 1-2 minutes until the sauce is smooth and coats the pasta completely.
Serve the Aglio e Olio spaghetti immediately. Sprinkle with finely chopped Italian parsley if desired. Enjoy!
