In a large oven-safe skillet, melt 2 tablespoons of unsalted butter with 1 tablespoon of olive oil over medium-low heat. Add 3 sliced yellow onions, sprinkle with 1 teaspoon of sugar and a pinch of salt. Cook slowly for 30-40 minutes, stirring frequently, until the onions are golden and caramelized. In the last minute, add 3 minced garlic cloves to enhance the aroma.

In a separate skillet, heat a tablespoon of olive oil over medium heat. Season 2 cups of cooked shredded chicken with salt and black pepper. Add the chicken to the skillet and brown it for about 5-7 minutes on both sides until golden, but don’t cook it fully as it will bake in the casserole later.

Once the onions are caramelized, carefully pour in 1 cup of low-sodium chicken broth to deglaze the skillet, scraping up any browned bits. Stir in 1 cup of orzo pasta, 1 cup of heavy cream, 1 teaspoon of dried thyme, and the browned chicken. Simmer the mixture over medium heat for 5-7 minutes until the orzo absorbs some of the liquid and is starting to soften.

Preheat your oven to 375°F (190°C). Stir in half of the 2 cups of shredded mozzarella into the orzo mixture, ensuring it melds into the creamy sauce. Transfer everything back into the skillet, then top with the remaining mozzarella. Bake for 20-25 minutes, or until the top is golden brown and bubbly.

Once baked, let the casserole rest for 5-10 minutes before serving. Garnish with fresh thyme or parsley if desired.