Meanwhile, put on the salted pasta water. Do not fully cook the penne in it. Chop fresh parsley. Add half the parsley to the sauce and add a few tablespoons of starchy pasta cooking water. Well, this step is indispensable, lift the penne out of the boiling water with a slotted spoon and combine it with the sugo in the pan, where it can simmer for a few more minutes and soak up all the flavors. This step creates the wonderfully creamy unity of sugo and pasta that is so typical of Penne all’Arrabbiata. Then generously add olive oil and stir in the remaining parsley. Refrain from all other supposed refinement measures. Neither pepper nor Parmesan belong in a Penne all’Arrabbiata, only Pecorino Romano is occasionally an exception in Lazio.