Preheat your oven to 180°C (350°F) and lightly grease a baking dish.
Peel and chop the potatoes into even-sized chunks. Slice the carrots and onion.
(Optional step) Parboil the potatoes for 5–7 minutes to help them cook faster and become extra soft in the bake. Drain well.
Add the potatoes, carrots, and onion to your baking dish and season with salt, pepper, garlic powder, and dried herbs. Toss to combine.
Pour over 300 mls of milk, making sure everything is lightly coated but not swimming in liquid.
Sprinkle in a little cheese and gently mix through.
Cover the dish with foil and bake for 30–40 minutes, until the vegetables start to soften.
Remove the foil, sprinkle the remaining cheese over the top, and return to the oven.
Bake uncovered for a further 10–15 minutes, or until the cheese is melted, golden, and bubbling.
Remove from the oven and let it sit for 5–10 minutes before serving to allow it to set.