Let’s walk through the steps to create this delightful dish, just like those mornings spent following Mum’s careful guidance in our Devon kitchen.

1. Preheat your oven to 350°F (175°C). Grease a 9×13 inch baking dish and set aside.
2. In a large skillet over medium heat, warm the olive oil. Add the chopped onion and minced garlic, sautéing until they become translucent, about 3-4 minutes.
3. Add the ground beef to the skillet, breaking it apart with a wooden spoon. Cook until browned, approximately 7-8 minutes. Drain any excess fat.
4. Stir in the cream of mushroom soup and milk, combining well. Season with salt, pepper, and thyme, and let it simmer for another 5 minutes.
5. Add the green beans and half of the shredded cheese to the mixture, stirring to combine.
6. Pour the beef and green bean mixture into the prepared baking dish, spreading it evenly.
7. Sprinkle the remaining cheese over the top, followed by the crispy fried onions.
8. Bake in the preheated oven for 25-30 minutes, or until the cheese is bubbly and golden brown.
9. Let the casserole cool for a few minutes before serving, allowing the flavors to meld beautifully.

The process is as much about the journey as it is about the destination, much like the stories mum would share as we cooked side by side.