Melt 2 tablespoons of unsalted butter and 1 tablespoon of olive oil over medium heat in a large skillet. Add 4 slices of yellow onions, sprinkle with 1 tablespoon of sugar and a pinch of salt. Sauté for 20-25 minutes until golden brown. Add 2 minced garlic cloves in the last 2 minutes.

In a separate skillet, heat 1 tablespoon of olive oil over medium-high heat. Season 2 cups of cooked shredded chicken with salt and black pepper. Add it to the hot skillet and brown for about 5 minutes without cooking through.

Once onions are caramelized, add chicken broth and scrape the skillet's bottom. Stir in 1 cup of orzo pasta, ½ cup of heavy cream, 1 teaspoon of dried thyme, and the browned chicken. Simmer for 5-7 minutes until orzo is slightly firm.

Preheat oven to 375°F (190°C). Stir in 1 cup of shredded mozzarella cheese until melted, transfer to a greased baking dish. Sprinkle remaining mozzarella on top and bake uncovered for 20-25 minutes until bubbling and golden.

Let the casserole rest for about 10 minutes before serving. Garnish with fresh thyme or chopped parsley. Enjoy your warm, creamy casserole.