Step 1

Preheat the oven to 350°F.

Step 2

Wash the potatoes and slice them thinly with a sharp knife, mandoline, or food processor. Cut the onion in half lengthwise, then in thin slices across.

Step 3

Butter a baking dish. Make layers of the potatoes and onions. Top each layer with thyme leaves, salt, and pepper. Finish with a layer of potatoes in an overlapping pattern.

Step 4

Pour the chicken or vegetable stock over, then cut the butter into small pieces and place them evenly on top of the last potato layer. Cover and bake for 1 hour or until the potatoes are soft all the way through.

Step 5

Uncover, raise the heat to 425°F and bake until the potato slices on top are golden brown.