Bring a large pot of salted water to a rolling boil. Add spaghetti and cook for 8-10 minutes until al dente.

While the pasta cooks, peel and slice garlic cloves. Heat olive oil in a skillet over medium heat and add garlic, cooking for 2-3 minutes.

Add red pepper flakes to the skillet, then add drained spaghetti along with a splash of reserved pasta water. Toss for 1-2 minutes.

Remove from heat and stir in chopped parsley. Grate Parmesan cheese on top if desired.

Serve in warm dishes, drizzled with more olive oil and additional red pepper flakes if desired.