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!
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
- Excellent side for Sunday night dinner or your holiday table
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:
- Simmer the leeks in a large skillet for about 20 minutes until they are cooked.
- In the meantime, thinly slice the potatoes and soak them in water.
- When the leeks are tender, add thyme, salt, pepper, and heavy whipping cream. Cook for another 5 minutes until the sauce gets thickened.
- Preheat your oven to 400°F.
- In a baking dish, layer one portion of the potatoes, then a portion of leek mixture, followed by cheese. Repeat for each layer.
- Sprinkle Panko and green onion on top.
- Cover with the aluminum foil and bake in the oven for 45 minutes.
- 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 Pork Roast
- Smoked Miso Butter Turkey Breast
- Arugula Salad with Fennel and Navel Orange
- Green Salad with Blood Orange Vinaigrette
Japanese Ingredient Substitution: If you want to look for substitutes for Japanese condiments and ingredients, click here.
- 3 Tbsp unsalted butter
- 2 stalks leeks
- 1 tsp kosher or sea salt (I use Diamond Crystal; use half for table salt)
- ¼ tsp thyme (fresh or dried)
- ⅛ tsp freshly ground black pepper
- ½ cup heavy whipping cream
- 2 cups Parmigiano-Reggiano (Parmesan) cheese (grated)
- 2 cups Mexican-style shredded cheese
- 1.5 lbs russet potatoes (3 potatoes)
- 1 Tbsp panko (Japanese breadcrumbs)
- 1 green onions/scallions (chopped, to garnish)
- Gather all the ingredients.
- Rinse the leeks and cut in half lengthwise. Chop into 1” (2.5 cm) pieces.
- Carefully wash the leeks again in running water.
- Butter a baking dish.
- In a large skillet, heat the rest of the butter on medium-high heat and add leek.
- Cover and let simmer for 20 minutes. Stir occasionally and cook until leeks are soft.
- Meanwhile, peel and slice the potatoes into ¼” (1.3 cm) pieces.
- Soak in water until you are ready to use them (prevent from changing color).
- When the leeks are soft, add thyme, salt, pepper, and heavy whipping cream. Simmer another 5 minutes until the sauce gets thickened.
- Preheat the oven to 400°F (200ºC). 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.
- Layer one portion of potatoes in the baking dish.
- Then layer one portion of the leek mixture.
- Layer one portion of each cheese. Repeat for each layer.
- Sprinkle panko and green onion on top. 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. Remove from the oven and let it sit another 15 minutes. Serve warm.
- You can keep the leftovers in an airtight container and store in the refrigerator for up to 3 days. The potato texture will change when frozen, so I do not recommend freezing this dish.