Finely chop onions, carrots and celery. Fry gently in oil. Add chopped pancetta. Fry for a few mins. Add finely diced potatoes
Add about half the stock. Then tomato puree. Cover and cook on lowest flame for about 25-30 mins. Add more stock if it's too dry. Stir occasionally
Add rest of stock (you may need a bit more stock or water) add pasta, cover and cook stirring occasionally. Check that it's cooking but the sauce must start to become dense. Add a good amount of Parmesan. Stir to make sauce creamy. When pasta is cooked and sauce is dense, serve with more Parmesan :)
