In a large skillet, pour in the olive oil and heat over medium heat. Once hot, add the thinly sliced onion. Sauté the onion, stirring occasionally, until it turns a deep golden brown and caramelizes, which should take about 15 to 20 minutes. Once caramelized, stir in the minced garlic and continue to cook for an additional 2-3 minutes until the garlic is fragrant and lightly golden.
In a spacious mixing bowl, combine the cooked orzo pasta, shredded chicken, chicken broth, and the sautéed onion and garlic mixture. Add in the dried thyme, dried rosemary, soy sauce, and season generously with salt and pepper. Mix everything together until well combined, ensuring the orzo is evenly coated with the flavors.
Carefully transfer the mixture into a greased 9x13-inch baking dish, spreading it evenly.
Top the orzo and chicken mixture by evenly sprinkling the shredded Gruyère and mozzarella cheeses across the surface, allowing for a satisfying cheesy crust.
Place the baking dish in the preheated oven and bake for 25-30 minutes, or until the cheese is bubbling and has developed a delightful golden hue.
Once baked, remove from the oven and allow the casserole to cool for a few minutes to set. Just before serving, garnish with the freshly chopped parsley for a burst of color and freshness.
Notes
Serve in individual bowls for a beautiful presentation.