1. Cook the tagliatelle in salted water according to package instructions. Drain the pasta.
2. Cut the bacon into cubes, fry in a pan, then add the chopped onion and parsley, season with salt and fry until the onions are glassy. Just before you turn off the heat, toss the finely chopped garlic into the frying pan and fry for a moment, taking care to not burn it.
3. Break the eggs into a bowl, beat lightly with salt and pepper and add the grated cheese. Toss the freshly drained pasta into the pan with the bacon, add the egg with cheese and heat until the sauce thickens, stirring constantly (you may heat it for longer, depending on your preferred sauce consistency). Serve the hot pasta on a plate and sprinkle with chopped parsley.