In Rome many years ago, I had this dish of humblest origins, and it has appeared on my table countless times since. I never tire of it – it is so good you want to inhale it. Over time, extra-virgin olive oil and pancetta have replaced the original lard and guanciale (pig's cheek cured like prosciutto, but sometimes used fresh). It is no less tasty this way, and young children seem to really like this dish. I don't know if the potato enhances the pasta or vice versa, I only know this dish could easily become a staple in your menu. It is particularly good accompanied by a stout red wine.
Heat the oil over medium heat in a small stockpot that will eventually hold everything. Add the pancetta and gently sauté until it is light gold in color. Add the onion and stir well. Lower the heat and cook the onion until it is translucent but not too soft.
Add the water and stir well. When the water comes to a simmer, add 1 teaspoon salt and the cubed potatoes. Stir well and cook for about 10 minutes.
Add the pasta and stir well. Let it cook for about 8 minutes more and then taste for salt. Correct it as needed, but remember the pecorino cheese will be salty – be careful. When the minestra is done, the potatoes should be soft but not mushy and the pasta should be al dente. Scatter on the chopped parsley and mix well.
Serve the minestra in hot bowls or soup plates. Grind on plenty of black pepper and sprinkle plenty of pecorino cheese on top.