Cook Rice & Prep Oven: Cook wild rice blend in seasoned chicken broth according to package directions (or use pre-cooked rice). Preheat oven to 375°F (190°C) and lightly butter a 9x13-inch ceramic baking dish.

Sauté Mushrooms & Aromatics: In a large Dutch oven or deep skillet, melt 3 tablespoons butter with olive oil over medium-high heat. Add sliced cremini mushrooms and cook undisturbed for 4 minutes until deeply browned. Add diced onion, carrots, and celery; sauté for 5 to 6 minutes until tender. Stir in minced garlic and fresh thyme for 60 seconds until fragrant. Transfer mushroom-veggie mixture to a large bowl.

Build the Scratch Mornay Sauce: In the same pot over medium heat, melt 4 tablespoons butter. Whisk in flour and cook for 2 minutes to eliminate raw flour flavor. Slowly pour in chicken bone broth and heavy cream while whisking vigorously to prevent lumps. Bring to a gentle simmer and cook for 4 to 5 minutes until thickened and velvety. Remove from heat. Whisk in Dijon mustard, 1 cup cheddar cheese, parmesan cheese, salt, and black pepper until completely melted and smooth.

Combine & Transfer to Dish: Add cooked wild rice, shredded chicken, and the sautéed mushroom-veggie mixture into the velvety cheese sauce. Fold together gently until every grain of rice and piece of chicken is coated. Spoon the mixture evenly into the prepared 9x13-inch baking dish.

Top with Cheddar & Garlic Panko: Scatter the remaining 0.5 cup sharp cheddar cheese over the top. In a small bowl, stir together panko breadcrumbs, melted butter, and garlic powder until damp and clumpy. Scatter the buttered panko evenly across the cheese layer.

Bake to Golden Crispy Bliss: Bake uncovered at 375°F (190°C) for 25 to 30 minutes until edges are vigorously bubbling and the panko topping is deeply golden brown and crunchy. (Broil on HIGH for 1 to 2 minutes if you want an extra-deep crust!). Rest for 10 minutes before scooping into generous portions. Garnish with chopped fresh parsley!