Preheat the oven to 200°C (400°F) or 180°C (350°F) for fan-forced ovens.

Arrange the potato slices neatly in a medium-sized baking dish, standing them vertically to create overlapping layers. This arrangement helps the cream seep between the slices for even flavor and tenderness.

In a mixing jug, whisk together the melted butter, heavy cream, minced garlic, sea salt flakes, and chicken or vegetable stock powder until well blended. Don’t worry if the butter slightly solidifies in the cold cream — it will melt beautifully during baking. Pour this creamy mixture evenly over the layered potatoes, ensuring each slice is well coated.

Sprinkle the thyme leaves over the top, followed by an even layer of shredded cheddar cheese. Cover the dish first with parchment paper to prevent the cheese from sticking, then tightly seal it with aluminum foil.

Bake the gratin for about 1 hour and 15 minutes, or until the potatoes are soft enough to pierce easily with a fork and the cream has thickened into a luscious sauce. Once tender, remove the foil and transfer the dish under the grill (broiler) for roughly 15 minutes, or until the surface turns golden and bubbly. Keep a close watch — it can brown quickly.

Remove from the oven and let it rest briefly before serving. Use a large spoon to scoop generous portions of the creamy, golden potato gratin, and serve warm as a comforting side or satisfying main dish.