Bring a large pot of salted water to a boil. Add the pasta and cook for 1 minute less than the package instructions.
In a large mortar, add the sun-dried tomatoes, walnuts, garlic and a pinch of salt. Crush with the pestle until a paste forms. Add the basil and pecorino and crush again. Drizzle in the olive oil and a pinch of red pepper flakes and mix and pound until a fairly smooth paste forms.
Drain the pasta, reserving a ladleful of pasta water, and combine the pasta with the pesto. Mix together and use a few splashes of pasta water to loosen the pesto. Serve garnished with some grated Parmesan (just a touch), fresh ground pepper and a drizzle of olive oil.
Important: Dose your sauce. Some people like the sauce thin, others like it very dense, which basically means less or more sauce that goes in the pasta. The tradition is to use a small ladle of the pasta water--the one you boiled the pasta in--and use it to dilute the sauce when you mix it in the pasta.