Bring a large pot of lightly salted water to a rolling boil and cook the spaghetti according to package directions until al dente.
While the pasta cooks, remove the chili seeds and finely chop the red chili. Peel and finely chop the garlic, removing the inner germ. Finely chop the parsley.
In a large bowl, combine the extra virgin olive oil with the chopped garlic and chili; season with salt and pepper and whisk with a fork to blend.
Reserve about 1 cup (240 ml) of the pasta cooking water, then drain the spaghetti.
Transfer the hot spaghetti to the bowl with the oil, garlic and chili. Add the grated pecorino and two tablespoons of the reserved cooking water, then toss quickly to form a creamy sauce, adding more cooking water as needed to reach a silky consistency.
Stir in the chopped parsley, toasted pine nuts, toasted slivered almonds and toasted breadcrumbs if using, mixing until evenly distributed.
Adjust seasoning with salt and pepper if needed and serve immediately.