Heat butter in a large deep skillet or Dutch oven over medium-high heat.
Add diced chicken and cook until browned on all sides, approximately 5 minutes. Remove chicken and set aside.
In the same skillet, add the diced onion and sauté for 3 minutes until translucent.
Add minced garlic and dry orzo pasta; stir constantly for 1 minute to lightly toast the pasta.
Pour in chicken broth and add dried thyme. Bring the mixture to a boil.
Reduce heat to low, cover, and simmer for 10 minutes or until orzo has absorbed most of the liquid.
Stir in heavy cream, frozen peas and carrots, and the cooked chicken.
Cook uncovered for 3-5 minutes, stirring frequently until the sauce reaches a creamy consistency.
Remove from heat, stir in Parmesan cheese, and season with salt and pepper to taste.