Preheat the oven to 350°F (175°C). Lightly grease a 9×13-inch baking dish.

Cook the wild rice blend according to its package directions. Set the cooked rice aside.

Pat the chicken pieces dry with paper towels. Season with 1/4 teaspoon each salt, black pepper, and paprika.

Heat 2 tablespoons olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat.

Arrange the chicken in a single layer. Sear without moving for about 1 minute, then continue cooking and stirring until the exterior becomes opaque. The chicken does not need to be completely cooked at this stage.

Using a slotted spoon, transfer the chicken to a large bowl.

Add the onion, carrots, and celery to the same pot. If the pot seems dry, add a small drizzle of olive oil or a little butter.

Sauté until the onion softens. Add the minced garlic and cook for another 30 seconds. Transfer the vegetables to the bowl with the chicken.

Melt 2 tablespoons butter with a small drizzle of olive oil in the same pot over medium-high heat.

Add the sliced mushrooms and toss briefly to coat. Arrange them in a single layer and cook until deeply golden and caramelized. Transfer them to the chicken and vegetable bowl.

For the cream sauce, whisk the chicken broth and cornstarch together in a measuring jug or bowl. Set aside.

In the same pot, melt 2 tablespoons butter with 1 tablespoon olive oil over medium heat.

Whisk in the flour and cook for approximately 2 minutes, whisking continuously.

Reduce the heat to low. Slowly whisk in the broth and cornstarch mixture, followed by the milk.

Add the Dijon mustard, halal-friendly Worcestershire sauce, chicken bouillon, dried parsley, basil, thyme, salt, and black pepper.

Bring the sauce to a gentle simmer, whisking frequently, until smooth and thickened.

Remove the pot from the heat. Stir in 1 cup of cheddar until melted, followed by the Parmesan.

Add the chicken, vegetables, mushrooms, and cooked wild rice to the creamy sauce. Stir gently until everything is evenly coated.

Taste and adjust the salt and black pepper as needed.

Transfer the Chicken Wild Rice Casserole mixture to the prepared baking dish. Sprinkle the remaining 1 cup cheddar evenly over the surface.

For the optional topping, melt 1 tablespoon butter with 1 tablespoon olive oil in a skillet over medium heat. Add the panko and cook, stirring frequently, until lightly golden.

Sprinkle the toasted panko evenly over the cheddar.

Cover the casserole and bake for 30–35 minutes, or until thoroughly hot and bubbling around the edges. Ensure the chicken reaches a safe internal temperature of 165°F (74°C).

Let the casserole rest for 5–10 minutes before serving.