Preheat oven to 350

Grease standard 12-cup muffin tin with cooking spray

Toss potatoes in half-in-half, garlic powder, pepper, thyme, salt and parmesan.

Divide potato mixture between muffin tin cups

Cover with foil and bake 40 minutes

Uncover muffin tin and top each stack with gruyere

Bake until cheese is melted and sides are beginning to turn golden, 20 minutes more