Preheat the oven to 160˚C.

In a saucepan, place the potatoes pieces, butternut squash, onion, garlic in a large wide saucepan and cover with water. Add some salt, and thyme. Bring to boil and simmer for 8-10 minutes until just softened.

Transfer the vegetables over onto a gratin dish. Check the seasoning. Pour over most of the liquid to ensure the vegetables are covered and sprinkle the cheese over.

Place in the oven for 35-40 minutes until cooked through and crispy.

Remove from the oven and serve immediately.