Preheat the oven to 375°F (190°C). Grease a 9×13-inch or similarly sized casserole dish.

Par-cook the diced potatoes: bring a pot of salted water to a boil, add the potatoes, and simmer 5–7 minutes until just fork-tender. Drain well.

Alternatively, microwave the diced potatoes in a covered dish for 4–6 minutes.

Heat the olive oil in a skillet over medium heat. Add the par-cooked potatoes and sauté 4–6 minutes to develop a little color; season lightly with salt and pepper. Remove from heat.

Steam or blanch the broccoli florets for 2–3 minutes until bright green and slightly tender. Shock in cold water to stop cooking, then drain.

In a large bowl, combine the cooked chicken, sautéed potatoes, broccoli, garlic powder, onion powder, cream (or milk), and half the shredded cheese. Mix until evenly coated. Taste and adjust salt and pepper.

Transfer the mixture to the prepared casserole dish. Sprinkle the remaining cheese evenly over the top.

Bake for 20–25 minutes, or until the casserole is bubbly and the top is golden.

If you like a crustier top, broil on high for 1–2 minutes watching carefully.

Let rest 5–10 minutes before serving so the sauce sets slightly.