I found these streaky bacon slices at the supermarket. They were already thinly cut, so the only thing I had to do was to cut the slices in two pieces to make the slices shorter.
Put 3 egg yolks plus 1 whole egg into a large bowl.
While whisking, add the Pecorino cheese, but add it gradually because the cheese will dry the mixture and you need a smooth and creamy mixture. In my case I added only 40 g (1 1/2 ounces) because 50 g (2 ounces) would have dried the mixture too much (the remaining cheese can be used later for topping the pasta if you like).
Take the crushed pepper you have previously prepared.
Add the pepper to the bowl.
Whisk until the mixture is smooth and creamy, and then leave it to rest.
Adding the oil...
Put the oil into a frying pan and when it is hot move the pan around distributing the oil all over the pan surface.
Lay all the bacon slices into the pan and cook at medium heat.
Cooking the bacon
After a minute or so, start stirring the slices in order to cook them on both sides. When you see the first sign of browning, remove the pan from the cooker and go to the next step.
Transfer the bacon slices into a small bowl and leave them for the moment. Now, put your spaghetti into the boiling water and while boiling start cooking the onion.
Get the onion rings
In the same pan you cooked the bacon slices, which is still hot, add the onion rings and cook them for a couple of minutes.
Then, add the wine and cook for a couple of minutes. Then, turn the heat down and gently cook the onions until caramelised.
This is what it should look like after a few minutes.
Remove the pan from the cooker and put the bacon slices back into the pan.
With the pan away from the cooker (we do not want to overcook the bacon), stir everything together and set aside.
When the spaghetti is ready, put the saucepan containing the bacon and the onion back on the cooker (low heat) and meanwhile drain the spaghetti (remember to leave the spaghetti a little wet). Be quick draining the spaghetti because we do not want it to cool down. Put the drained spaghetti back into the large pan you used to boil it, which is still hot, and quickly add the bacon and onions.
Stir quickly for 10 seconds and move on to the next stage.
Get the egg mixture
Quickly add the egg mixture.
Stir everything together for 20 seconds. The heat of the spaghetti and the heat of the pan is enough to cook the egg mixture. Do not carry out this procedure on the cooker otherwise, you will dry the spaghetti too much (I do not think you want to reach this stage to have spaghetti and scrambled eggs!). The final result should be a creamy sauce coating the spaghetti. Please, do not use any cooking cream, milk or butter; these are "tricks" that people use to cover their mistakes (even in Italy!).
Serve immediately and feel free to season with more pepper if you like, or sprinkle with some of the remaining Pecorino cheese, if you have any left. You can also try garnishing the plate with some parsley (flat leaf - torn by hand), but not too much.