1. Cut the bacon into small cubes.
2. Beat the egg yolks in a bowl and add the grated cheeses.
3. Brown the diced bacon in a non-stick pan, on a medium heat. Set aside.
4. Boil the spaghetti in plenty of boiling water.
5. Before draining, remember to set aside a spoonful of pasta water to better toss and stir pasta and sauce.
6. Drain the pasta al dente, toss in the pan with the bacon. Then take off the heat and add the beaten egg yolks.
7. Don’t cook them too much- let the egg yolks thicken slowly, adding a little of the cooking water if necessary.
8. Season with freshly ground black pepper and serve.