Preheat your oven to 375°F (190°C) and lightly grease a baking dish.
In a large mixing bowl, combine the shredded cooked chicken with pumpkin puree, milk, chopped vegetables, ground cinnamon, salt, and pepper. Mix everything until smooth and well integrated, creating a creamy filling.
Stir in the shredded cheese to the mixture, folding gently so it melts slightly into the filling, adding richness and gooey texture.
Pour the filling into the prepared baking dish, spreading it out evenly with the back of a spoon or spatula.
In a small bowl, mix the bread crumbs with melted butter until evenly coated, creating a crispy topping.
Sprinkle the buttery bread crumbs evenly over the top of the casserole, covering the filling completely.
Place the casserole dish in the oven and bake for about 30 minutes, or until bubbling around the edges and the topping is golden brown.
Remove from the oven and let it rest for 5 minutes; then, serve hot, revealing a creamy, textured filling topped with crispy crumbs.