Bring a saucepan of salted water to the boil and cook the spaghetti. In the meantime, dice the streaky bacon; peel the clove of garlic and crush it lightly. Put the oil in a pan and fry the clove of garlic and the diced bacon briskly so that they turn golden brown all over. Put the eggs in a bowl, add the grated Parmesan and Pecorino cheese, season with a pinch of salt and pepper and mix together gently with a whisk or a fork. Drain the spaghetti when it is “al dente”, pour into the pan with the bacon and mix together with a wooden spoon; remove the pan from the heat, add the egg and cheese mixture and season with freshly ground black pepper and mix together gently so that all the ingredients blend: if the sauce is too thin, place the pan on a medium heat once again for a few seconds.