Cook the spaghetti al dente (it should have a bite to it) in a small amount of well-salted water. Reserve about a ½ cup of the pasta cooking water (!).
Prepare the ingredients: finely chop the garlic (do not use a garlic press), roughly chop the anchovies, drain and rinse the capers, and cut the olives in half.
Heat the olive oil and butter in a large frying pan, add the garlic, chili flakes, and anchovies, cook over medium-low heat, stirring, for 1 minute.
Add the olives, capers, crushed tomatoes/passata, and pasta cooking water. Bring to a boil, reduce the heat to low and cook for 15 minutes (stirring from time to time) until the sauce is thickened. After this time, season the sauce lightly with salt and pepper. Be careful with adding salt, because anchovies, olives, and capers are already salty. Take the pan off the heat.
Add the cooked pasta to the pan, toss with the sauce.
Sprinkle with chopped parsley, grated parmesan, and serve immediately.
Enjoy!