01 -
In a saucepan over medium heat, melt the butter. Add the minced garlic and sauté until golden and fragrant, about 1–2 minutes. Pour in the heavy cream and bring to a gentle simmer. In a separate small bowl, whisk together the flour with ⅓ cup of water until smooth. Slowly add this mixture to the saucepan, whisking constantly to avoid lumps. Return the saucepan to heat and stir in salt, pepper, and thyme. Once the sauce thickens slightly, remove it from the heat and mix in the shredded Gruyère until fully melted. Set aside.
02 -
Preheat your oven to 400°F (200°C). Grease a casserole dish with softened butter. Arrange a layer of thinly sliced potatoes in the dish, slightly overlapping. Sprinkle lightly with salt and pepper. Repeat with additional layers until all the potatoes are used.
03 -
Pour the prepared cheese sauce evenly over the layered potatoes, ensuring every slice is coated. Cover the dish tightly with foil and bake for 1 hour and 15 minutes.
04 -
Remove the foil, sprinkle the remaining Gruyère cheese over the top, and bake uncovered for an additional 5 minutes. For a golden, bubbly finish, broil on high for 3–5 minutes, watching closely to prevent burning.
05 -
Let the dish rest for 5–10 minutes. Garnish with chopped chives, if desired, and serve warm.