Cut bacon and onion into bite-sized pieces.
Cook the spaghetti noodles in boiling water.
Add olive oil to a pan and sauté the bacon and onion.
Add the cooked noodles to the pan and stir-fry together.
In a bowl, mix egg yolk, Parmigiano cheese, pepper, and cream.
Remove the pan from heat and combine all ingredients with the sauce.
Top with cheese and parsley to finish.