Although scalloped potatoes ... would also complement au gratin. Or, you can borrow ideas from tartiflette -- another cheesy potato dish -- and toss in some cubed up ham or bacon for a little ...

Finish by topping with remaining potato mixture (making sure to add all the cream), Gruyère, and Parmesan; reserve remaining 1/2 tsp. thyme. Bake potato gratin until golden brown on top and bubbling, ...