Preheat your oven to 375°F (190°C). Grease a casserole dish. Yes, this matters more than you think.
In a large bowl, mix the chicken, broccoli, onion, garlic, cheese, soup, milk, sour cream, and seasonings. Stir until everything looks uniformly delicious.
Spread the mixture into the prepared dish. Smooth the top so it bakes evenly and looks photogenic for your Instagram story.
In a small bowl, mix breadcrumbs with melted butter. Sprinkle over the casserole for a golden, crunchy crown.
Bake for 25–30 minutes, until bubbling around the edges and the top is golden brown. If you want extra browning, switch to broil for a minute—but keep a close eye so you don’t burn it.
Let it rest for 5 minutes, then slice and serve. This helps it set, so you don’t have soup on your plate.