by MEGHAN SPLAWN
Au gratin potatoes are one of the greatest casseroles of all time. I’d dare to say au gratin potatoes are better than even the best mashed potatoes — and they’re easier, too.
Heat the oven to 400ºF. Coat a 9x13-inch baking dish with unsalted butter.
Grate 8 ounces Gruyère or sharp cheddar cheese.
Thinly slice 3 pounds potatoes and 1 small onion, and mince 2 garlic cloves.
Make the cheese sauce on a stovetop by adding flour, Dijon mustard and salt and pepper to melted butter and the garlic, then whisking in milk and the cheese until the cheese melts.
Layer the potatoes, onions, and cheese sauce in the baking dish.
Bake uncovered for 60 to 75 minutes.
Cool the gratin for 10 minutes before scooping and serving.