1. Preheat your oven to 350°F (175°C). Lightly grease a 9×13-inch baking dish with butter or oil.
2. In a large skillet over medium heat, melt the butter with olive oil. Add the sliced onions and a pinch of salt. Cook slowly, stirring occasionally, until the onions are golden brown and caramelized — about 30 to 40 minutes. This step is key; don’t rush it. The deep, sweet flavor of the onions is the heart of this casserole.
3. Once the onions are beautifully caramelized, add the garlic and thyme. Cook for another minute until fragrant.
4. In a separate pan, brown the ground beef over medium-high heat until no longer pink, breaking it up with a wooden spoon. Drain excess fat if needed.
5. Combine the caramelized onions and garlic mixture with the browned beef in the same skillet. Stir in Worcestershire sauce, salt, and pepper to taste. Let it simmer together for 5 minutes so the flavors meld.
6. Pour in the beef broth and bring the mixture to a gentle boil. Stir in the rinsed rice, cover, and simmer on low heat for 15 minutes, or until the liquid is mostly absorbed and the rice is just tender. It should still have a little bite since it will finish cooking in the oven.
7. Remove the skillet from heat and stir in the sour cream and half of the shredded cheese. Adjust seasoning if needed.
8. Transfer everything to your prepared baking dish. Sprinkle the remaining cheese evenly over the top.
9. Bake uncovered for 25-30 minutes, or until the cheese is melted, bubbly, and golden on the edges.
10. Remove from the oven and let it rest for 5 minutes before serving. Garnish with fresh parsley for a pop of color and freshness.

I remember my first time caramelizing onions for a big family dinner — it felt like magic, watching them transform from sharp and crisp to sweet and silky. It’s that slow patience, that attention to detail, that makes this casserole more than just a meal. It’s a story you get to taste.