Cook bacon in a large skillet over medium heat until crisp, about 5 minutes. Transfer to paper towels to drain. Add onion to bacon drippings in skillet; cook until tender, 3 to 5 minutes.
Meanwhile, cook ramen in a saucepan according to package directions, adding peas the last minute of cooking. Reserve 1/2 cup cooking water; drain.
Whisk together egg, Parmesan, onion and drippings, salt, and red pepper in a bowl. Add hot ramen and cooked bacon. Toss to coat, adding enough reserved cooking water to make a creamy consistency. Top servings with parsley.
