Place a pan over medium heat and add a small amount of butter or oil. Once heated, add the chicken pieces in a single layer so they cook evenly. Let them cook without moving for a minute or two to develop a light golden color, then stir occasionally. Season with salt and pepper as they cook. Continue cooking until the chicken is fully done, no longer pink in the center, and slightly golden on the outside. Remove from heat and set aside so it stays juicy.

Bring a pot of water to a gentle boil or set up a steamer. Add the broccoli florets and steam them for a few minutes until they turn bright green and are just tender when pierced with a fork. Be careful not to overcook them—you want them to remain slightly firm so they hold their texture in the casserole. Once done, remove immediately and let them cool slightly.

In the same pan or a clean one, melt butter over medium-low heat. Add the minced garlic and sauté gently, stirring continuously for about 30–60 seconds until it becomes fragrant. Avoid letting it brown, as burnt garlic can turn bitter and affect the flavor of the entire dish.

Pour in the heavy cream and add the softened cream cheese. Stir slowly and consistently, allowing the cream cheese to melt into the cream. Keep the heat moderate and continue mixing until the sauce becomes completely smooth, creamy, and slightly thickened with no lumps remaining.

Add the shredded cheddar cheese to the sauce in small handfuls, stirring after each addition. Allow it to melt fully before adding more. This helps create a smooth, velvety texture rather than a clumpy sauce. Continue stirring until the sauce is rich, thick, and fully combined.

In a large mixing bowl, add the cooked chicken and steamed broccoli. Pour the warm cheese sauce over them. Gently fold everything together using a spoon or spatula, making sure all pieces are evenly coated without breaking the broccoli too much.

Lightly grease a baking dish to prevent sticking. Transfer the mixture into the dish and spread it out evenly, smoothing the top so it cooks uniformly. Make sure the ingredients are distributed evenly for consistent texture in every bite.

Sprinkle the mozzarella cheese evenly over the top, covering the entire surface. This layer will melt and form a golden, slightly crispy topping during baking, adding both flavor and visual appeal.

Place the baking dish in a preheated oven at 180°C (350°F). Bake for about 20–25 minutes, or until the top is melted, bubbly, and lightly golden. If you prefer a more browned top, you can leave it in for a few extra minutes, but keep an eye on it to prevent burning.

Remove the casserole from the oven and let it rest for about 5 minutes before serving. This allows the sauce to settle and thicken slightly, making it easier to serve while keeping the texture creamy and cohesive.