Heat oil in a large skillet over medium heat. Saute onions in oil until tender. Drain on paper towels.
Using the same pan, cook mushrooms in butter over medium heat. Stir in onions and bacon; reduce heat to low, and cook until bacon browns. In a medium bowl, beat together eggs, cream, and cheese; mix into bacon mixture. Cook, stirring, until the sauce begins to thicken. Remove from heat.
Meanwhile, cook pasta in a large pot of boiling water until done. Drain. Toss hot noodles with sauce, parsley and red pepper flakes.