Preheat your oven to 375°F (190°C).
In a large skillet, heat the olive oil over medium heat. Add the diced onion and cook until translucent, about 3-4 minutes.
Stir in the minced garlic and cook for an additional 1 minute until fragrant.
Add the diced chicken to the skillet and cook until browned and cooked through, about 5-7 minutes.
Mix in the diced carrots, frozen peas, thyme, rosemary, salt, and pepper. Cook for another 3-4 minutes until the vegetables are tender.
Pour in the chicken broth and heavy cream, stirring to combine. Bring the mixture to a simmer.
Add the cooked orzo to the skillet and stir until well combined. Remove from heat.
Transfer the mixture to a greased 9x13 inch baking dish. Sprinkle the cheddar and Parmesan cheese evenly over the top.
Bake in the preheated oven for 20-25 minutes, or until the cheese is bubbly and golden brown.
Remove from the oven and let it cool for 5 minutes. Garnish with chopped parsley before serving.