Preheat the oven to 375°F (190°C).
Wash and peel the potatoes, then slice them thinly (about 1/8 inch thick).
In a saucepan, combine the heavy cream, minced garlic, salt, and pepper; heat gently.
Grease a 9x13-inch baking dish with butter.
Layer half of the sliced potatoes in the prepared dish, followed by half of the cream mixture and a sprinkle of thyme, then half of the cheddar cheese.
Repeat with the remaining potatoes, cream mixture, thyme, and cheese, finishing with a generous layer of cheese on top.
Dot the top with remaining butter before covering the dish with aluminum foil.
Bake in the preheated oven for 40 minutes, then remove the foil and bake for an additional 20 minutes until the top is golden brown and bubbly.
Let the dish rest for 10 minutes before serving.