Boil the pasta in lots of salty water, the more water you use, the better the pasta will be, even for a small quantity.
Drain the pasta and let it stand until your sauce is ready.
To save time, start preparing your sauce while the pasta is boiling.
For the sauce: in a frying pan, fry the onions and garlic with the pancetta until the onions are golden brown and the pancetta is crispy. Do not use more than a few drops of oil, or even none at all, because the pancetta will give you plenty of that.
Toss the pasta with the fried onions, garlic and pancetta.
Pour cream over it all, as much as you like (I use about 100 ml).