I was first introduced to broth-based potato gratins as a young chef at Boston’s historic Parker House restaurant. We served them often because diners loved them, and their straightforward composition—potatoes, thyme, chicken broth, onions, and cheese—complemented everything from roast chicken to standing rib roast.
Years later, I still make this kind of gratin at home and at work. I like the fact that you can put it together quickly with items that are usually on hand, yet it’s also elegant enough for a formal dinner party. The soft, layered potatoes and crisp Gruyère crust create a rich side dish that’s also relatively light—compared to a traditional creamy gratin. That’s a welcome thing around the holidays, when heavy foods are seemingly everywhere.
Russets and a rest are the keys to perfect texture
To punch up the flavor of canned chicken broth, I brown onions and then add the broth to them to infuse it and to pick up the caramelized juices on the bottom of the pan. The browned onions (a quick version of caramelized onions) give depth to the broth, and they’re easy to make. I sauté sliced onions over medium heat to soften them; then I raise the heat to high and stir rapidly until they brown and sweeten, about 15 minutes total cooking time.
Russet potatoes are a good fit for this gratin. Their starchiness helps bind the layers and is a good base for absorbing the flavorful broth. To make slicing the wobbly potatoes easier, I first take a thin slice off their bottoms so that they rest flat against the cutting board, and then cut them into thin disks, between 1/8 and 1/16 inch thick.
After baking the gratin, let it sit for 20 minutes before cutting so it has a chance to set. This cooling period allows the potatoes to soak up the remaining broth and the layers to tighten up, so you can slice perfect square pieces. The resting period also gives you a chance to finish your other dinner preparations.
Other flavors, as you like
This gratin is delicious as it is, but you can certainly dress it up. Adding bacon and sautéed bell peppers, a nod to the classic potatoes O’Brien, lends a meaty sweetness. You can substitute chopped parsley or chives for the thyme or add oven-roasted tomatoes, fresh rosemary, and olives for a more robust version. You could also use a different cheese for the Gruyère if you like. Monterey Jack or a good aged Cheddar work well, though you may want to add them halfway through baking, as they melt more quickly than Gruyère.