A crisp potato cake would be tempting enough—even without the surprise of garlicky kale sandwiched between its layers.
Cooks' note:
Galette can be made 6 hours ahead and cooled, uncovered, then kept, on a baking sheet covered with foil, at room temperature. Remove foil, then reheat in a 425°F oven until heated through and crisp, about 20 minutes.