Leek and Onion Scalloped Potatoes Recipe

Okay, my friends, get ready to fall in love. I mean, head-over-heels, write-a-love-song, can’t-stop-thinking-about-it OBSESSED. Today, we are making Leek and Onion Scalloped Potatoes, and I swear, it’s going to change your life. If you’re a fan of cozy, creamy dishes, you must try my velvety French potato and leek potage next.

This isn’t just a side dish. This is a creamy, dreamy, cheesy flavor explosion. It’s the dish that makes everyone at the table go completely silent, except for the happy little “mmm” sounds. It’s elegant enough for your fanciest dinner party but cozy enough for a Tuesday night. Are you ready? Let’s do this!

Recipe Overview

Cuisine: American/French-Inspired
Category: Side Dish
Prep Time: 25 minutes
Cook Time: 1 hour 15 minutes
Total Time: 1 hour 40 minutes
Servings: 6-8 people

Do You Love This Recipe Too?

I have a confession. I once made this for a potluck and literally hid a portion in the back of the fridge for myself before I left the house. That’s how good it is.

I just knew my friends would devour it all. And they did! The pan was scraped clean. This recipe is my ultimate secret weapon for making people feel loved and fancy, all at the same time. The combo of leeks and onions is pure magic.

My Shopping List for This Recipe

This dish is all about simple, beautiful ingredients coming together. The star players are the potatoes, leeks, and a good, melty cheese. Here’s what you need to grab!

Let’s Get Your Ingredients Ready

Lay everything out on your counter. It makes the whole process so much smoother and more fun, I promise! If you’re looking for another fantastic way to use potatoes, my garlic butter steak and potatoes skillet is a one-pan wonder.

3 lbs Yukon Gold potatoes (about 6-7 medium)
2 large leeks
1 large yellow onion
3 cloves garlic, minced
3 tbsp unsalted butter
3 tbsp all-purpose flour
2 ½ cups whole milk
1 cup heavy cream
1 ½ cups shredded Gruyère cheese (divided)
½ cup grated Parmesan cheese
1 tsp fresh thyme leaves (or ½ tsp dried)
½ tsp freshly grated nutmeg
Salt and black pepper to taste

Bringing This Recipe to Life (Step-by-Step)

This is where the magic happens! Don’t rush the sauce. Giving it a little love makes all the difference.

Preheat your oven to 375°F (190°C). Butter a 9×13 inch baking dish. Get your potatoes ready by scrubbing them clean. You can peel them if you want, but I love leaving the skins on for texture!
Slice the potatoes very thinly, about 1/8-inch thick. A mandoline slicer is a huge help here for even cooking. Place the slices in a big bowl of cold water to prevent browning.
Now, the alliums! Trim the dark green tops and roots off your leeks. Slice them in half lengthwise and rinse under cold water, fanning the layers to get all the grit out. Slice them thinly. Do the same with your yellow onion.
In a large pot or Dutch oven, melt the butter over medium heat. Add the sliced leeks and onion. Cook for 10-12 minutes, stirring often, until they are super soft and sweet. Add the garlic and cook for one more minute until fragrant.
Sprinkle the flour over the cooked veggies. Stir constantly for about 2 minutes to cook the raw flour taste out. This is your roux—the base of our incredible sauce!
Slowly pour in the milk and cream, whisking constantly to avoid lumps. Bring the mixture to a gentle simmer. Let it cook for 3-5 minutes until it thickens nicely. It should coat the back of a spoon.
Turn off the heat. Stir in 1 cup of the Gruyère, all of the Parmesan, thyme, nutmeg, a big pinch of salt, and lots of black pepper. Taste it! This is the best part. Adjust the seasoning until it’s perfect for you.
Drain your potato slices and pat them dry with a clean kitchen towel. This is key for a creamy, not watery, bake.
Pour a thin layer of the sauce into the bottom of your prepared dish. Arrange a third of the potato slices in an even layer. Spoon a third of the remaining sauce over them. Repeat layers two more times, ending with sauce.
Sprinkle the remaining ½ cup of Gruyère cheese over the very top. Cover the dish tightly with foil.
Bake, covered, for 45 minutes. Then, remove the foil and bake for another 25-30 minutes until the top is gloriously golden brown and the potatoes are tender when pierced with a knife.
Let it rest for 15 minutes before serving. I know, the wait is torture! But it lets everything set up so you get perfect slices.

Fun Variations to Try Next Time

Once you master the classic, play around! It’s so fun to make it your own.

Bacon Lover’s Dream: Cook 6 slices of chopped bacon until crisp. Sprinkle it between the potato layers for a smoky, salty crunch.

Herb Garden Twist: Swap the thyme for other fresh herbs. Tarragon or chives would be amazing with that mild onion flavor.

Extra Cheesy & Crispy: Mix some panko breadcrumbs with a little melted butter and Parmesan. Sprinkle it on for the last 10 minutes of baking for an insane crunchy top.

How to Store, Freeze, and Reheat

Got leftovers? Lucky you! Here’s how to keep the joy going.

Let the bake cool completely. Store it covered in the fridge for 3-4 days. To reheat, cover with foil and warm in a 350°F oven until heated through. You can also microwave single portions.

To freeze, assemble the dish but do not bake it. Wrap it tightly in plastic wrap and foil. Freeze for up to 2 months. Thaw in the fridge overnight, then bake as directed, adding a little extra time if needed.

NUTRITION INFORMATION

Calories: ~420
Carbohydrates: 38g
Protein: 15g
Fat: 24g
Saturated Fat: 14g
Fiber: 4g
Sugar: 8g

A Quick Q&A on This Recipe

Can I make this ahead of time?

Absolutely! Assemble the whole dish, cover it, and pop it in the fridge for up to 24 hours before you need to bake it. You might need to add 5-10 extra minutes to the baking time since it will be cold from the fridge.

What’s the best potato to use?

I am team Yukon Gold all the way! They have the perfect balance of starch and waxiness. They hold their shape but also get beautifully creamy. Russets will work, but they can get a bit more mealy.

My sauce seems too thick/thin. Help!

Don’t panic! If it’s too thick right after making it, just whisk in a splash more milk. If it seems too thin, let it simmer for another minute or two. It will also thicken up a lot as it bakes with the potatoes.

There you have it! My ultimate, most cherished, show-stopping side dish. Every single time I make it, I remember why I love cooking so much. It’s about creating something beautiful and delicious that brings people together.

This recipe is a hug on a plate. It’s the taste of spring and comfort all in one. I am so excited for you to try it and make your own memories around the table. For another deeply comforting bowl, my wild mushroom, caramelized onion, and kale soup is pure earthy goodness. Now go forth and bake something incredible!

I can’t wait to hear how yours turns out! Did your family go crazy for it? Did you try a fun variation? Please leave a comment and a rating below to let me know what you think!

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