Preheat oven to 375 degrees F.
Lightly grease a 9-inch square baking dish and set aside.
To cook rice, combine 2 cups chicken stock, water, and rice in a medium saucepan. Bring to a simmer, cover and cook until tender, about 1 hour. Drain rice and transfer to a large bowl.
Heat olive oil in a medium skillet. Add onion and celery and season with salt, Essence, and black pepper. Cook until softened, about 5 minutes. Add parsley and thyme and cook another minute. Remove from the heat and add to bowl with rice.
Add 4 cups of crumbled Cornbread to the rice mixture and stir to combine. Transfer rice mixture to baking dish. Drizzle remaining 1/2 cup chicken stock and butter over mixture. Bake until cornbread is golden and crispy, about 20 minutes.