In a large oven-safe skillet, melt 2 tablespoons of unsalted butter and 1 tablespoon of olive oil over medium heat. Add 2 large yellow onions, 1 tablespoon of sugar, and 1 teaspoon of salt, stirring frequently. Cook for 20–25 minutes until the onions turn a deep golden brown and are tender. Stir in 2 minced garlic cloves during the last 2 minutes for added flavor.

Once the onions are perfectly caramelized, add 1 cup of orzo pasta to the skillet and sauté for 2 minutes to toast it slightly. Then, mix in 2 cups of cooked, shredded chicken, 1 teaspoon of dried thyme, and a pinch of black pepper. If desired, add a splash of Worcestershire sauce for extra richness. Stir all the ingredients together until well combined.

Next, carefully pour in 3 cups of low-sodium chicken broth and 1 cup of heavy cream. Increase the heat to bring the mixture to a gentle simmer. Cover the skillet and reduce the heat, allowing it to cook for about 8–10 minutes, stirring occasionally, until the orzo is tender and has absorbed some of the liquid.

Once the orzo is cooked and creamy, stir in 1 cup of shredded mozzarella cheese and ½ cup of grated Parmesan cheese. Continue to mix until the cheeses are fully melted and the sauce becomes extra creamy.

Preheat your oven to 375°F (190°C). Sprinkle the remaining 1 cup of mozzarella cheese evenly over the top of the casserole for a bubbly finish. Bake uncovered for 10–15 minutes, or until the cheese is melted, bubbly, and turns a light golden color, creating a delicious crust.

Once baked, allow the French Onion Chicken Orzo Casserole to rest for 5–10 minutes before serving. Optionally, garnish with fresh thyme or parsley for a touch of color and freshness before enjoying this comforting dish.