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Potato Leek Gratin ポテトとリークのグラタン

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    This simple casserole is loaded with thin slices of creamy potatoes, savory leeks, and generous handfuls of cheese. It’s amazingly good that you want to make extra for leftovers! 

    A baking dish containing Potato Leek Gratin

    There are quite a few potato gratin dishes we enjoy in Japan, but this was the first time I tried cooking it with leeks. Have you cooked with them before? Leeks are like giant green onions, but with a milder flavor. The slightly sweet yet savory and distinct herbaceous aroma is absolutely wonderful when paired with a cheesy potato gratin dish.

    My family absolutely loves this Potato Leek Gratin. With a deep golden brown top, it’s nearly impossible not to go back for a second bite.

    Why You’ll Love This Potato Leek Gratin

    • Super comforting and decadent
    • A perfect make-ahead side dish
    • Vegetarian-friendly
    • Excellent side for Sunday night dinner or your holiday table

    A baking dish containing Potato Leek Gratin.

    Potatoes & Leeks – The Golden Combination

    Some foods are meant to go hand in hand. Like Potatoes and leeks! They pair perfectly together that you can never go wrong no matter how you cook them. Potatoes with their smooth velvety texture and leeks with their savory depth. Together they make a great soup and a mouthwatering casserole!

    How to Make The Gratin

    This Potato Leek Gratin is really simple. Here are the steps involved:

    1. Simmer the leeks in a large skiller for about 20 minutes until they are cooked.
    2. In the meantime, thinly slice the potatoes and soak in water.
    3. When the leeks are tender, add thyme, salt, pepper, and heavy whipping cream. Cook for another 5 minutes until the sauce gets thickened.
    4. Preheat your oven to 400°F.
    5. In a baking dish, layer one portion of the potatoes, then a portion of leek mixture, followed by cheese. Repeat for each layer.
    6. Sprinkle Panko and green onion on top.
    7. Cover with the aluminum foil and bake in the oven for 45 minutes.
    8. Remove the cover, and broil for 2-3 minutes until the top is glossy and golden brown.

    What to Serve with Potato Leek Gratin

    I usually serve this  Potato Leek Gratin as a side to go with roast meat or fish. It certainly makes a special Sunday meal, but also elegant enough to serve on your holiday dinner. If you’re looking for menu inspiration for the holidays, I’d suggest serving the gratin with:

    Japanese Ingredient Substitution: If you want to look for substitutes for Japanese condiments and ingredients, click here.

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    5 from 4 votes
    A baking dish containing Potato Leek Gratin.
    Potato-Leek Gratin
    Prep Time
    20 mins
    Cook Time
    1 hr
    Total Time
    1 hr 20 mins

    This simple casserole is loaded with thin slices of creamy potatoes, savory leeks, and generous handfuls of cheese. It's amazingly good that you want to make extra for leftovers! 

    Course: Main Course
    Cuisine: Japanese
    Keyword: creamy, gratin, leek, potato
    Servings: 4
    Author: Namiko Chen
    • 3 Tbsp unsalted butter
    • 2 stalks leeks
    • 1 tsp kosher/sea salt (I use Diamond Crystal; Use half for table salt)
    • ¼ tsp thyme (fresh or dried)
    • freshly ground black pepper
    • ½ cup heavy (whipping) cream
    • 2 cups Parmigiano-Reggiano (Parmesan) cheese (grated)
    • 2 cups Mexican-style shredded cheese
    • 3 russet potatoes (3 potatoes = 1.5 lbs)
    • green onions/scallions (chopped, to garnish)
    • 1 Tbsp panko (Japanese breadcrumbs)
    1. Gather all the ingredients.

      Potato-Leek Gratin 1
    2. Rinse the leeks and cut in half lengthwise. Chop into 1” pieces.
      Potato-Leek Gratin 2-a
    3. Carefully wash the leeks again in running water.
      Potato-Leek Gratin 2-b
    4. Butter a baking dish.
      Potato-Leek Gratin 3
    5. In a large skillet, heat the rest of the butter on medium-high heat and add leek.

      Potato-Leek Gratin 4-a
    6. Cover and let simmer for 20 minutes. Stir occasionally and cook until leeks are soft.

      Potato-Leek Gratin 4-b
    7. Meanwhile, peel and slice the potatoes into ¼” pieces.
      Potato-Leek Gratin 5-a
    8. Soak in water until you are ready to use them (prevent from changing color).

      Potato-Leek Gratin 5-b
    9. When the leeks are soft, add thyme, salt, pepper, and heavy whipping cream. Simmer another 5 minutes until the sauce gets thickened.

      Potato-Leek Gratin 6-b
    10. Preheat the oven to 400°F. Divide the potatoes, leek mixture, and each cheese according to your baking dish size. I divided them in half as my baking dish is shallow.

    11. Layer one portion of potatoes in the baking dish.
      Potato-Leek Gratin 7-a
    12. Then layer one portion of the leek mixture.

      Potato-Leek Gratin 7-b
    13. Layer one portion of each cheese. Repeat for each layer.
      Potato-Leek Gratin 7-c
    14. Sprinkle Panko and green onion on top.

      Potato-Leek Gratin 8
    15. Cover with the aluminum foil and bake for 45 minutes. To check whether the dish is done, test by inserting a skewer through the foil. If the skewer is able to go through the potato smoothly then it’s ready. Remove the cover and change the oven setting to broil. Broil for 2-3 minutes until golden brown on top. Be careful not to broil for too long since you don’t want to burn the dish.

    16. Remove from the oven and let it sit another 15 minutes before it’s ready to serve.

    Recipe Notes

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