First, put the pasta in salted cooking water and cook according to the instructions on the packet.
Then peel the onion, dice it and fry it in hot olive oil until translucent, then add the bacon (if you use a very lean bacon, it should be warmed up shortly before the pasta is ready, otherwise it will harden).
Meanwhile, beat the eggs in a soup plate and whisk. When the eggs are completely mixed together, mix in the milk and the grated Parmesan. The whole thing should be light yellow in color, but it is better to use less milk than too much.
Drain the pasta and add to the pan with onions and bacon. Take the pan off the heat and pour the egg, milk and cheese mixture over it. Mix well, but make sure that the whole egg doesn`t stick to the bottom. In the end, each noodle should be coated with the sauce.