Preheat your oven to 350°F (175°C).
In a large skillet, heat the olive oil over medium heat. Add the diced onions and sauté until they are translucent, about 3-4 minutes.
Add the ground beef to the skillet. Cook until browned, breaking it up with a spoon, about 6-8 minutes. Drain excess fat if necessary.
While the beef is cooking, bring a large pot of salted water to a boil. Cook the egg noodles according to package instructions until al dente. Drain and set aside.
In a mixing bowl, combine the cream of mushroom soup, sour cream, shredded cheddar cheese, thawed peas, and carrots. Stir well until all ingredients are evenly mixed.
Add the cooked ground beef and onions to the mixing bowl. Season with garlic powder, salt, and black pepper. Mix until well combined.
Gently fold in the cooked egg noodles until everything is evenly mixed.
Pour the entire mixture into a greased 9x13 inch baking dish. Spread evenly across the dish.
Bake in the preheated oven for 25-30 minutes, or until the casserole is bubbly and the top is lightly golden.
Remove from the oven and let it cool for a few minutes. Garnish with fresh parsley if desired before serving.