Choosing the greatest potato dish of all time is an impossible task. Frankly, there are far too many options and they’re all irresistible. But choosing my favorite potato dish to make? That’s an entirely different story, and the answer comes easily: a cheesy potato gratin. Potato gratins are quick to prepare and always crowd-pleasers. But what I love most about them is that their simplicity allows for endless spontaneity: You can switch up the potatoes, cheeses, and spices however you fancy. What some might see as a simple side, I see as a blank canvas, and I consider this particular rendition my Mona Lisa. Inspired by the flavors of ranch dressing, this zesty potato casserole is just as creamy and rich as the original, but a little bit tangier and far more herbaceous. When served warm and bubbling from the oven, it’s nearly impossible to resist. Here’s how to do …