Potato Leek Gratin – The Almond Eater

April 11, 2024

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This Potato Leek Gratin is a creamy and cozy side dish you’ll want at every weeknight dinner. With layers of buttery potatoes, tender leeks, and a ridiculously delicious cheese sauce in every bite, it’s completely irresistible!

a serving of potato leek gratin on a plate with a fork

Whether you’re planning an extravagant holiday meal or a casual weeknight dinner, this Potato Leek Gratin needs to be on the menu. It’s a totally crowd-pleasing side dish with layers of savory and cheesy flavors in every bite! Best of all, the ingredients are friendly to your wallet but still yield restaurant-quality results.

Just like my vegan cauliflower gratin, this au gratin side dish drowns fresh veggies (leeks and potatoes) in a luscious cheese sauce before it’s baked in the oven. The result? Creamy bites of pillow-soft potatoes and subtly sweet leeks you can pair with endless main dishes.

Recipe features

This potato and leek gratin is a filling comfort food that bakes tender Yukon gold potatoes and savory leeks in a rich and creamy sauce.
Who can resist golden, bubbling cheese on top and buttery potatoes below? Not me! This dish is a crowd-pleaser wherever and whenever you serve it.
Enjoy it as a comforting side dish or as a creamy main dish!

Ingredients

Yukon gold potatoes – These are my go-to potatoes for au gratin side dishes because they always turn out to be perfectly tender and buttery while still holding their shape. If you can’t find Yukon gold’s, use Russet potatoes instead.

Leeks – Leeks are part of the onion family, but they aren’t as strongly flavored as white or red onions. Instead, they’re mild and sweet, similar to green onions.

Herbs and seasonings – I seasoned the leeks, potatoes, and cream sauce with salt, freshly ground black pepper, fresh thyme sprigs, and a bay leaf. Feel free to experiment with more herbs and seasonings, like fresh rosemary, paprika, or fresh dill.

Milk and cream – These are used as the base of the cheese sauce. Together, they make every bite incredibly luscious and rich! You can try using only milk here, but the sauce won’t be as thick, potentially making the gratin loose and more liquid-y.

Dijon mustard – Just 1 teaspoon helps emulsify the sauce and gives it a tangy and sharp bite.

Cheese – I used both Gruyère and Parmesan in the cheese sauce, so there’s no shortage of cheesy flavor!

Chives – Fresh chopped chives on top add a refreshing onion-y flavor, complementing the leeks perfectly.

Instructions

Step 1: Slice and arrange the potatoes. Slice the peeled potatoes, then toss them in a bowl with the salt and black pepper. Arrange the slices in a single layer on the bottom of a prepared casserole dish. Continue layering until you run out of potatoes.

sliced potatoes in a glass bowl with salt and pepper on top

Step 2: Cook the leeks. Melt the butter in a skillet over medium heat. Add the leeks, salt, pepper, and thyme, then cook until the leeks have softened. Discard the thyme sprigs and spoon the leeks over the potatoes.

Step 3: Make the sauce. Add the milk, heavy cream, garlic, mustard, and bay leaf to the now-empty skillet. Simmer the sauce until it thickens slightly, then discard the bay leaf.

Step 4: Bake. Pour the sauce over the potatoes and leeks, then top with both kinds of cheese. Cover the dish with foil and bake until the top layer of cheese is golden brown and bubbly. Set it aside to cool before garnishing the dish with fresh chives. Enjoy!

2 images: the left image shows potato leek gratin with grated cheese on top and the right image shows the potato leek gratin baked and out of the oven

Tips and FAQs

For the most even potato slices, slice the potatoes with a mandoline or a sharp chef’s knife.
For cheesier bites, sprinkle shredded Gruyère and/or Parmesan cheese in between each layer of potatoes.
Try to avoid reduced or low-fat dairy options for this recipe. Full-fat is the way to go because it’s the most rich and flavorful!

Tip

Always wash the leeks well before cooking! After they’re sliced, dump them into a bowl of water and move them around to loosen any dirt or debris. Drain and pat them dry with a paper towel, then cook as normal.

Variations

Add more veggies – Like spinach, sliced sweet potatoes, or chopped broccoli.
If you can’t find leeks – Make this with scallions, shallots, chives, or sweet onions instead.
Use a different kind of cheese – Swap the gruyère with Comté, Fontina, cheddar, or Swiss cheese instead.
Top with breadcrumbs – For that perfect golden and crunchy finish, top the leek and potato bake with about 1 cup of buttered breadcrumbs during the last 15 minutes of baking.

Serving suggestions

If you want to turn this casserole into a full-blown meal, I recommend serving it on the side of your favorite proteins. It pairs well with simple baked salmon fillets or Mediterranean cod. For heartier appetites, serve it next to these pan-seared chicken breasts, pot roast, or creamy garlic chicken.

For a well-rounded dinner, pair the potato and leek bake with your favorite proteins and a few simple side dishes, like garlic bread, asparagus soup, and garlic broccoli steaks.

Need to use up the leftovers? Try folding a scoop into an egg white frittata or heat it up and enjoy it with classic scrambled eggs!

What does “au gratin” mean?

“Au gratin” translates to “by grating” or sometimes “with a crust” in French. An au gratin dish is traditionally topped with a golden layer of cheese and/or breadcrumbs. Potatoes au gratin, for example, is a classic dish that tops thinly sliced potatoes with a creamy cheese sauce.

Do you have to peel the potatoes?

No, not if you don’t want to. I like the more uniform look of the potato rounds without the skin, but you can save a bit of time on prep and cleanup by leaving the skins on.

Storage

Refrigerator: Once the leftovers are cooled to room temperature, transfer them to an airtight container and store them in the fridge for up to 3 days.

Freezer: I don’t recommend freezing the leftovers because the sauce is so dairy-heavy. After thawing, you’ll likely see a lot of separation, and the texture won’t be as rich and creamy.

potato leek gratin in a casserole dish with a piece taken out

More casserole recipes

If you made this potato leek gratin recipe, be sure to leave a comment and star rating below. Thanks!