Cook the fettuccine in a large saucepan of salted boiling water, following packet directions, until al dente.
Meanwhile, heat the oil in a large frying pan over medium-high heat. Add onion and garlic and cook, stirring often, for 4 minutes or until soft. Add mushrooms and cook for 4 minutes or until mushrooms are tender.
Drain the fettuccine and return to the hot saucepan. Whisk eggs in a bowl with a fork until well combine. Quickly add the eggs, mushroom mixture, parmesan and parsley to the hot fettuccine and toss over low heat until well combined (the heat from the pasta is enough to cook the egg, don’t let it scramble). Season with salt and pepper and serve.
Servings 4