Preheat oven to 350 degrees.  Butter a 9 x 13 inch baking dish.  

Mix heavy cream, melted butter, and crushed garlic together.  

Spread out ⅓ of the sliced potatoes in the baking dish, pour over ⅓ of the heavy cream mix. Scatter a handful of the cheese over and ⅓ of the thyme leaves. Sprinkle with a layer of salt and pepper.  

Repeat layer two more times.  

Add extra cheese over top, if desired.  

Cover with tin foil and bake for 1 hour. Uncover and bake an additional 30 minutes, or until the potatoes are tender when pierced with a knife and golden brown on top.  

Remove from oven and allow to rest for 15 minutes before serving.