<p>Grease a round cake pan with a diameter of 20 cm. Line the bottom of the pan with parchment paper and lightly grease it.</p><p>In a medium saucepan, heat the olive oil over medium heat. Add the shallot, cook for about 20 minutes, until they are candied. Incorporate the thyme.</p><p>Place a layer of potato slices, slightly overlapping them in the pan. Lightly salt and pepper, add a layer of shallot, then drizzle with a bit of broth.</p><p>Repeat the operation with the remaining potatoes and broth, seasoning each layer. Pour the remaining broth on top. Cover the pan with a greased sheet of parchment paper, press down lightly on the potatoes, then cover with a sheet of aluminum foil.</p><p>Bake the gratin in the center of the oven until the potatoes are tender.</p>