Preheat the oven to 350°F (175°C).
In a medium saucepan, bring 4 cups of water to a boil. Add the rice, reduce heat to low, cover, and simmer for 15-20 minutes until rice is tender and water is absorbed. Remove from heat and fluff with a fork.
While the rice is cooking, heat the olive oil in a skillet over medium heat. Add the chopped onion and sauté for 4-5 minutes until translucent.
Add the minced garlic to the skillet and cook for an additional 1 minute until fragrant. Remove from heat.
In a large mixing bowl, combine the cooked rice, sautéed onion and garlic, cooked chicken, Campbell’s Cream of Mushroom Soup, Campbell’s Cream of Chicken Soup, sour cream, shredded cheddar cheese, frozen peas, black pepper, salt, and dried thyme. Stir until all ingredients are well incorporated.
Transfer the mixture to a greased 9×13 inch casserole dish and spread evenly.
Sprinkle the grated Parmesan cheese evenly over the top of the casserole.
Cover the casserole dish with aluminum foil and bake in the preheated oven for 40 minutes.
Remove the foil and bake for an additional 15 minutes uncovered, until the top is golden brown and bubbly.
Remove from the oven and let the casserole rest for 5 minutes before serving.