A classic Italian-American weeknight pasta dish. This is essentially a poor man's pasta, traditionally made with all the leftover pieces of pasta and a starchy potato like russets.
In a large saucepan, add uncured pancetta, then raise the heat to medium. Slowly fry the pancetta to golden brown, about 8 minutes.
Stir in the chopped onion to the pan, and saute until soft, about 5 minutes. Then stir in the minced garlic and saute for 2 more minutes.
Stir in the tomato paste and saute for 3 minutes. Stir in the chopped potatoes until well coated.
Pour in the stock, water, and salt, and bring to a simmer. Lower the heat to medium-low, cover, and simmer for 20 minutes. Open and stir occasionally to prevent the potatoes from sticking. They're done when you can use the back of a spoon to smash the potatoes.
Add the pasta and mix well. Simmer uncovered for 15 minutes, stirring often to prevent the pasta from sticking. Stir in the parsley and parmesan and serve.
Notes
Always fry pancetta starting from a cold pan. Raise the heat to medium and slowly fry the pancetta until golden-brown.
Caramelize the tomato paste before adding the potatoes. Let it sit in the pan and it will intensify the tomato flavor.
Potatoes and pasta have a tendency to stick to the pan. Stir often to keep them from sticking, especially when you first add the pasta.