Bring a large pot of water to a boil and season generously with salt. Cook the spaghetti until al dente (according to package instructions). While the pasta is cooking, thinly slice the garlic. Heat the olive oil over medium heat and gently fry the garlic until golden brown (be careful not to overcook it). Add the chili and cook for 10-15 seconds. Drain the pasta, reserving 2-3 tablespoons of the cooking water. Add the spaghetti to the skillet with the oil and toss. Add a little of the pasta water for added moisture. Remove from heat and garnish with parsley and Parmesan cheese, if desired.
Serve immediately, hot. Pairs perfectly with a green salad and a glass of dry white wine.