Get Ready: Preheat your oven to 400°F (200°C). Lightly grease a 9x13 inch casserole dish, then spread the cooked shredded chicken evenly at the bottom.
Sauté Leeks & Mushrooms: In a large skillet, warm up 1 tablespoon of butter and 1 tablespoon of olive oil over medium heat until hot. Add the sliced leeks and sauté until they are soft and fragrant, about 5-7 minutes. Then, add the sliced white mushrooms and cook until they are tender, about another 5 minutes.
Layer It Up: Carefully spoon this delicious leek and mushroom mixture over the chicken in your casserole dish. You can leave any extra liquid in the skillet for the sauce.
Whip Up the Sauce: Into the same skillet, add the beef broth, cubed cream cheese, sour cream, salt, and pepper. Stir well over medium heat until the sauce is smooth and creamy. For an extra velvety sauce, you can use an immersion blender briefly. Pour this rich sauce evenly over the chicken and vegetable layers.
Add the Crispy Topping: In a small bowl, combine the pork rind crumbs with the melted butter. Sprinkle this savory topping generously over the casserole.
Bake to Perfection: Bake in the preheated oven for 20-25 minutes, or until the casserole is bubbly and the topping is golden. Let it rest for a few minutes before serving.