In a large oven-safe skillet, melt 2 tablespoons of butter and 1 tablespoon of olive oil over medium heat. Add 3 thinly sliced yellow onions, 1 teaspoon of sugar, and a pinch of salt. Cook for 20–25 minutes, stirring occasionally, until the onions become golden brown and caramelized. In the last minute, stir in 2 cloves of minced garlic until fragrant.

Once the onions are perfectly caramelized, add 1 cup of orzo pasta to the skillet and toast it for about 2 minutes, stirring frequently.

Stir in 2 cups of shredded rotisserie chicken, 1 teaspoon of dried thyme, and freshly ground black pepper to taste. If desired, add 1 tablespoon of Worcestershire sauce for extra depth. Mix everything thoroughly.

Pour in 4 cups of low-sodium chicken broth and 1 cup of heavy cream, stirring to combine. Increase the heat slightly to bring the mixture to a gentle simmer and cover the skillet. Cook for about 8–10 minutes, until the orzo is tender.

Remove the skillet from heat and stir in 1 cup of shredded mozzarella cheese and ½ cup of grated Parmesan cheese until melted.

Preheat your oven to 375°F (190°C). Sprinkle the remaining 1 cup of mozzarella cheese over the top of the casserole. Bake uncovered for 10–15 minutes until the cheese is bubbly and golden brown.

Remove the skillet from the oven and let the casserole rest for about 5–10 minutes before serving.