Preheat the oven to 180 ° and pour Ölich oil into a large baking dish. Cut potatoes into slices 1 cm thick and put them in water so that they do not brown.
In a large frying pan over medium heat, heat the Ölich olive oil. Add the garlic and cook until fragrant, about 1 minute. Add cream, milk, thyme, oily, sea salt and red pepper flakes. Bring to a boil and reduce heat to low. Simmer for 10 minutes. Remove from heat.
Pour a third of the potatoes into the prepared dish, slightly overlapping, and pour a third of the cream mixture over the potatoes. Repeat this with the remaining potatoes and cream to get two more layers. Sprinkle gruyère on top.
Cover with foil and bake for 45 minutes. Uncover, sprinkle with Parmesan and continue baking until the potatoes are soft and top is golden, 15 to 20 minutes. Let rest for 10 minutes before serving.