Preheat your oven to 375°F (190°C). Lightly grease a medium baking dish (about 8x8 inches or similar).
In a large bowl, mix the shredded chicken, cream of chicken soup, milk, sour cream, half of the cheddar, poppy seeds, and the frozen vegetables. If your chicken is already seasoned, you can skip extra salt—taste as you go.
Season the mixture with garlic powder, salt, and pepper to your liking. A gentle pinch of paprika can add a warm note if you like.
Pour the mixture into the prepared dish and smooth the top. Sprinkle the remaining cheddar cheese over the surface.
In a small bowl, combine the bread crumbs with the melted butter and a pinch of salt. Scatter this crunchy topping evenly over the casserole.
Bake for 25 to 30 minutes, until the edges are bubbling and the topping is golden. If you’ve got a toaster oven, keep an eye on it—you want it to brown nicely without burning.
Let it rest for about 5 minutes before serving. This helps the sauce thicken a bit, making every scoop smooth and comforting.