1. Preheat your oven to 350°F (175°C) and grease a 9×13 inch baking dish.
2. In a large skillet, heat the olive oil and butter over medium heat. Add the sliced onions and cook, stirring occasionally, until they are caramelized and golden brown, about 15-20 minutes.
3. In a large mixing bowl, combine the thawed hash browns, cream of mushroom soup, sour cream, shredded cheddar cheese, garlic powder, dried thyme, and half of the caramelized onions. Season with salt and pepper to taste.
4. Transfer the mixture to the prepared baking dish, spreading it out evenly. Top with the remaining caramelized onions and French fried onions.
5. Bake in the preheated oven for 45 minutes, or until the top is golden brown and crispy.
6. Let it cool for a few minutes before serving, allowing the flavors to meld beautifully.

These steps reflect the care and attention I learned in my grandmother’s kitchen, where every dish was a labor of love and a testament to our heritage. Remember, the key to this recipe is patience, especially when caramelizing the onions to achieve that perfect depth of flavor.