This is what gets made in this kitchen at midnight, after the last table has left and everyone is too tired to think about anything more complicated than a pot of water and whatever's already open in the pantry. Garlic, olive oil, and chili, and nothing else needed.
Serves 4.
Bring a large pot of water to a boil, and salt it properly -- about ten grams of salt per liter, enough to taste clearly seasoned. Cook the spaghetti until just short of al dente; it will finish in the pan.
While the pasta cooks, warm the olive oil in a wide skillet over low heat, and add the garlic and chili. Cook gently, stirring often, until the garlic turns pale gold -- not brown, and certainly not the deep amber that means it has already gone bitter. This takes patience more than skill; low heat is the entire technique here.
Scoop out at least a cup of the pasta water before draining. Add the drained spaghetti directly to the pan with the garlic oil, and toss vigorously over low heat, adding pasta water a little at a time until the oil clings to the strands rather than pooling at the bottom of the pan. Stir in the parsley, and serve immediately.
If the dish tastes bitter throughout, the garlic browned too far before you noticed -- there is no saving a batch of burnt garlic; discard the oil and start again, watching it more closely this time. If the oil pools at the bottom of the bowl instead of coating the pasta, you didn't add enough pasta water, or didn't toss it vigorously enough to build the emulsion. And if the dish tastes flat despite everything going right, be more generous with both the garlic and the chili next time -- this is a dish with almost nothing to hide behind, and timidity is the most common way to ruin it.