Bring 4.5 litres/8 pints water to the boil in a large saucepan with eight teaspoons salt. Add the spaghetti and cook for nine minutes, or until al dente.
Meanwhile, cut the pancetta into lardons (short little strips), about 6mm/1¼in wide.
Heat a large, deep frying pan over a medium-high heat, add the oil and the pancetta and fry until lightly golden. Add the garlic and parsley and cook for a few seconds, then remove from the heat and set aside.
Drain the spaghetti well, tip into the frying pan with the pancetta, garlic and parsley, add the beaten eggs and half the grated pecorino cheese and toss together well.
Season to taste with a little salt and black pepper. The heat from the spaghetti will be sufficient to partly cook the egg, but still leave it moist and creamy. Take to the table and serve in warmed pasta bowls, sprinkled with the rest of the cheese.