In a mixing jug, melt the unsalted butter over medium heat, then add finely minced garlic and cook for about 1 minute until fragrant. Pour in the thickened cream and stir well to combine.

Preheat your oven to 180°C (350°F).

Peel your starchy potatoes and slice them into 1/8-inch (3 mm) thick rounds, placing them in a bowl of cold water to prevent browning.

In a 1.5-liter (6 cup) baking dish, layer the sliced potatoes, starting with a third of the potato slices, followed by a drizzle of the cream mixture, and sprinkle with salt, black pepper, and fresh thyme.

Cover the baking dish tightly with aluminum foil and place it in the preheated oven. Bake for approximately 1 hour and 20 minutes until the potatoes are fork-tender.

After baking, remove the foil and arrange the cold brie slices evenly on top of the potato mixture. Return to the oven uncovered and bake for an additional 30 minutes.

Once out of the oven, let the dish rest for about 5 minutes before serving.