Slice the potatoes into 1/8 inch thick slices and set aside.
In a small saucepan, melt the butter over low heat and add minced garlic; cook for 1 minute.
Add the milk to the saucepan, stirring until combined, then remove from heat.
In a small bowl, mix together salt, pepper, and thyme.
Grease a 9x13 inch baking dish. Place a third of the potato slices in the dish, sprinkle with a third of the salt, pepper, thyme, and cheese. Repeat for second layer.
In the final layer, evenly place remaining potato slices, pour the milk mixture over the top, sprinkle remaining salt, pepper, thyme, and top with cheese.
Cover with foil and bake for 90 minutes until potatoes are tender. Remove foil, add remaining cheese, and bake for an additional 10 minutes.
Let stand and cool slightly before serving.
Notes
This classic potatoes au gratin is a comforting side perfect for family dinners or special occasions.