Creamy Potato Leek Casserole: Dauphinois Gratin

Potato Leek Casserole combines thinly sliced potatoes, garlic-scented butter, sautéed leeks, rich cream and Gruyère cheese, then bakes until golden and bubbling for an elegant, comforting side dish.

Potatoes and leeks are a classic pairing. Their mild, sweet flavors complement each other beautifully; add cream and Gruyère and you get a creamy, savory casserole that’s both familiar and elevated. This dish echoes the flavors of potato-leek soup but in a hearty gratin form — perfect for weeknight dinners, holiday tables, or any time you want a comforting, crowd-pleasing side.

How to make this Potato Leek Casserole?

Making this casserole is straightforward. Follow these steps for a creamy, cheesy gratin with tender leeks:

Heat 2 tablespoons butter in a skillet, add cleaned and chopped leeks, and sauté over medium heat until very soft, about 10 minutes.
Add 2 cups heavy cream, salt, pepper, and fresh thyme; simmer until the cream thickens slightly, about 3–4 minutes, then remove from heat.
Peel and slice potatoes (Russet or yellow potatoes work well) into 1/8-inch slices using a mandoline or a sharp knife.
Rub the inside of a cast iron skillet or a casserole dish with a halved garlic clove, then coat with 2 tablespoons of butter.
Layer the potatoes in the prepared dish, spooning one-third of the leek-and-cream mixture over the first layer and sprinkling with 1/2 cup grated Gruyère, salt, pepper, and a bit of thyme.
Repeat to make three layers, using all of the leek mixture and most of the cheese; reserve a little cheese for the top.
Cover tightly with foil and bake in a preheated 350°F (175°C) oven for 40 minutes. Remove the foil and bake another 10 minutes until the cheese is golden and bubbly and potatoes are tender.
Allow the casserole to rest for 10 minutes before serving so it sets and slices neatly.

Scroll down for the full printable recipe details including exact ingredients, times and notes.

What to serve this Potato Leek Casserole with?

This casserole is versatile and pairs beautifully with roasted or grilled meats, poultry, fish, or a simple green salad. It works equally well as a vegetarian main when served with roasted vegetables or a composed grain salad. Its rich, creamy texture makes it especially suitable for holiday meals and special occasions, where it can be a luxurious side alongside roast turkey or chicken.

Suggested pairings include roasted turkey, baked chicken, braised beef, or simply a crisp winter green salad to cut the richness. The casserole’s elegant presentation and familiar flavors make it an excellent choice for both everyday dinners and festive gatherings.

How does this Potato Leek Casserole taste?

The flavor is creamy and savory with a gentle sweetness from the leeks and a nutty, slightly salty finish from the Gruyère. If you enjoy the classic potato-leek soup (vichyssoise) you’ll recognize those same comforting notes here, amplified by the cheese and the slow baking process that concentrates flavors. Texture-wise, expect tender, layered potato slices cushioned in a luscious cream sauce with a golden, cheesy top.

This dish recalls elevated scalloped potatoes with an aromatic leek twist. It’s rich but balanced, and a spoonful will deliver both comfort and refinement. Serve warm, and allow it to rest before serving so it slices cleanly and retains its creamy structure.

Potato Leek Casserole

This recipe is adapted from classic potato dauphinois with the addition of sautéed leeks for a fuller, more aromatic flavor. Rich, decadent and elegant, it makes a memorable side for holidays or any special meal.

Ingredients

2 pounds Russet or yellow potatoes, peeled and cut into 1/8-inch slices
2 leeks, trimmed, washed and chopped
1 garlic clove, halved
4 tablespoons butter
2 cups grated Gruyère cheese (or Cheddar as a substitute)
2 cups heavy cream
2 teaspoons fresh thyme
Salt and pepper to taste

Instructions

Trim leeks and chop into small pieces. Place in a bowl of water and swish to remove sand; lift out with a slotted spoon and drain on paper towels.
Melt 2 tablespoons of butter in a skillet over medium heat. Add leeks and sauté, stirring often, until very soft, about 10 minutes.
Add the cream, salt, pepper and thyme; simmer until slightly thickened, 3–4 minutes. Remove from heat.
Slice potatoes into 1/8-inch rounds using a mandoline or sharp knife.
Rub the garlic cut-side around the inside of a 9-inch round or 8×8-inch square baking dish or cast iron skillet, then spread 2 tablespoons butter to coat.
Arrange a layer of potato slices in the bottom of the dish. Spoon one-third of the leek-cream mixture over the potatoes, sprinkle with salt, pepper, 1/2 cup of cheese and one-third of the thyme.
Repeat to make two more layers, finishing with the remaining cheese on top.
Cover tightly with foil and bake in a preheated 350°F (175°C) oven for 40 minutes. Remove foil and bake another 10 minutes or until cheese is golden and bubbly and potatoes are tender when pierced with a knife.
Let rest 10 minutes before serving to allow the casserole to set.

Notes

1. Russet potatoes are preferred for a creamier texture, but yellow potatoes work well too. 2. If Gruyère is unavailable or costly, substitute a good melting Cheddar or another flavorful melting cheese.

Nutrition (per serving)

If you enjoy this recipe, try other potato-based sides such as Potato Leek and Feta Pie, New Dill Potatoes with Scallion Cream Sauce, Maple Mashed Sweet Potatoes with Candied Pecans, or European-style Potato Pancakes for more variety and inspiration.