Creating a perfect Potato Gratin is simple if you follow these steps:

1. Preheat Oven: Set your oven to 375°F (190°C).
2. Prepare the Baking Dish: Grease a baking dish (about 9×13 inches) with butter and set aside.
3. Slice Potatoes: Peel the potatoes and slice them thinly (about 1/8 inch thick) using a mandoline or sharp knife.
4. Mix Dairy: In a bowl, combine the heavy cream, whole milk, minced garlic, thyme, salt, and pepper. Mix well.
5. Layer Potatoes: Begin layering the sliced potatoes in the prepared baking dish, slightly overlapping them for even baking.
6. Add Cheese: After adding a couple of layers, sprinkle a layer of grated cheese over the potatoes. Repeat this process until all potatoes are layered.
7. Pour Cream Mixture: Once the final layer of potatoes is placed, pour the cream mixture evenly over the dish, ensuring all potatoes are coated.
8. Top with Cheese: Add any remaining cheese on top for that golden crust.
9. Little Extra Crunch: For a crispy topping, you can sprinkle breadcrumbs over the cheese (optional).
10. Bake: Cover the dish with aluminum foil and bake in the oven for 40 minutes. Then, remove the foil and bake for an additional 20 minutes, or until golden brown and bubbly.
11. Cool and Serve: Allow the gratin to cool slightly before serving. This will help it firm up a bit for easier slicing.

These steps will guide you through making a delectable Potato Gratin, ensuring that each bite is filled with rich, silky goodness.