Creating the French Onion Beef Casserole is straightforward when you follow these easy steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C).
2. Cook the Beef: In a large skillet over medium heat, brown the ground beef until fully cooked. Drain any excess fat.
3. Sauté Onions and Garlic: Add the sliced onions to the same skillet and cook until soft and golden, about 15 minutes. Stir in the minced garlic and cook for an additional 1-2 minutes.
4. Mix in Liquids: Pour in the beef broth, soy sauce, Worcestershire sauce, thyme, salt, and pepper. Stir until well combined.
5. Cook the Noodles: In a separate pot, cook the egg noodles according to package instructions. Drain and set aside.
6. Combine Ingredients: In a large bowl, mix the cooked noodles with the beef mixture and sour cream until everything is thoroughly blended.
7. Layer in Casserole Dish: Pour half of the mixture into a greased 9×13 inch casserole dish. Sprinkle half of the Swiss cheese on top. Add the remaining beef mixture and top with the remaining Swiss cheese and Parmesan cheese.
8. Bake: Cover the casserole with aluminum foil and bake in the preheated oven for 30 minutes. Remove the foil and bake for another 15-20 minutes until the cheese is bubbly and golden.
9. Cool: Remove the casserole from the oven and let it cool for about 10 minutes before serving.

These steps will guide you in creating this incredible dish effortlessly.