Cook the fettuccine in a large saucepan of salted boiling water, following packet directions, until al dente.
Meanwhile, heat 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 fettuccine and return to saucepan. Whisk eggs in a small bowl with a fork. Add eggs, mushroom mixture, parmesan, parsley and salt and pepper to fettuccine and toss until well combined.
Place saucepan over medium heat and toss for 1 minute or until egg mixture has just set. Serve immediately.