For the casserole: Cook wild rice according to package directions, until rice splits and curls into a "c" shape, exposing its chewy interior. Drain, if needed, and set aside.

While the wild rice is cooking, proceed with the rest of the recipe. In a large pot over medium to medium-high heat, melt 4 tablespoons of the butter. Add the mushrooms, onion, carrots, and celery. Stir occasionally until the onions are translucent and the carrots are softened, about 10–15 minutes. Stir in the garlic and cook for 2 minutes more.

Preheat oven to 375°F. Then sprinkle the flour over the vegetables in the pot and stir to incorporate. Cook for 2 minutes.

Stir in the chicken broth and bring the mixture to a gentle boil. Cook for 4–5 minutes, until nicely thickened. Stir in the half-and-half and cook for another 2 or 3 minutes to thicken again.

Add the soy sauce, parsley, thyme, salt, and pepper, stirring to combine. Then fold in the drained wild rice and chicken. Add the Gruyere and Parmesan, and fold to combine. Taste and adjust with additional salt and pepper, if desired.

Transfer chicken wild rice mixture to a large casserole dish. Cover with a lid or piece of foil, and cook for 20–25 minutes, or until it starts to bubble.

For the crouton topping: Remove casserole from oven and top with bread cubes, leaving the outer edge of the casserole exposed. Slowly drizzle a fine line of melted butter over the tops of the bread cubes, aiming to hit as many of the bread cubes as possible. Sprinkle top of buttery bread cubes evenly with the 1/4 teaspoon of kosher salt and the 1/4 cup of Parmesan. Return casserole to the oven, uncovered, and bake for an additional 15 minutes, or until bread cubes are nicely browned and the casserole is hot and bubbling. Remove from oven, sprinkle with additional fresh parsley and thyme, and serve immediately