Bring a large pot of water to a rolling boil. Add 10 g of salt per liter of water.

Drop in the spaghetti and cook until al dente according to package instructions, usually 8 to 10 minutes.

While the pasta cooks, pour the olive oil into a cold skillet, add the sliced garlic, and set over medium-low heat.

Cook the garlic, stirring occasionally, for about 2 to 3 minutes until slices turn pale gold and fragrant. Do not let them brown.

Add the chili flakes, stir once, and immediately remove the pan from the heat.

Scoop out 120 ml of pasta water and set it aside before draining the spaghetti.

Drain the spaghetti well and set aside briefly.

With the skillet off the heat, pour in 80 ml of the reserved pasta water. Swirl the pan vigorously until the water and oil look creamy and slightly emulsified.

Add the drained spaghetti to the skillet and return to low heat.

Toss constantly with tongs for 60 seconds, adding extra pasta water one tablespoon at a time if the sauce looks dry, until every strand is coated in a glossy, pale sauce.

Remove from heat, fold in the parsley if using, taste for salt, and serve immediately in warmed bowls with a drizzle of raw olive oil over the top.