Ultra Cheesy Potato Gratin Side Dish (Au Gratin Potatoes)

Think of the creamiest, cheesiest mac and cheese you've ever had. Now, instead of noodles, imagine that sauce on potatoes! In this ultra cheesy potato gratin recipe, that's exactly what you get: the cheesy potatoes of your dreams that make the perfect holiday side dish.

Whether you call them potatoes au gratin, au gratin potatoes, or just potato gratin, they're cheesy, they're potatoes, and they're delicious!

What makes them different from scalloped potatoes is the addition of cheese. And what doesn't get better with cheese? 

Now, if you're here, you might be on the lookout for Thanksgiving or Christmas recipes amidst a million other things you need to do. You've got a LOT going on this time of year. So let's skip the small talk and dive into the details. 

Cheesy potato gratin ingredients 

Here's what you'll need to create these mac and cheese-like potatoes for yourself!

• Large Yukon gold or russet potatoes (I use four large potatoes, about 900 g)
• Diced white onion
• Unsalted butter
• Flour
• Salt and pepper
• Garlic cloves
• Whipping cream (I use cream because you get a richer, creamier result than with just milk!)
• Freshly shredded old/sharp cheddar cheese (don't use pre-shredded cheese, here's why)
• Mustard powder
• Garlic powder
• Onion powder
• ¼ cup finely shredded parmesan (optional)
• A sprinkle of parsley for garnish (optional but adds great colour!)

With the help of a mandolin slicer, this is a reeeeeally easy recipe! Just practice patience while you add the cream to the roux (if you add it too fast, the sauce won't come together as nicely), and follow the rest of my instructions.

How to make my ultra cheesy potato gratin for yourself

• Begin by turning your oven on to 350 F.
• Now start melting butter in a large skillet on medium heat WITH the diced onions and minced garlic cloves.
• Once the butter is melted and the onions have softened, whisk in the flour, salt and pepper, mustard powder, onion powder, and garlic powder until it forms a paste–this takes about one minute.
• SLOWLY add the cream to the mixture a bit at a time. Keep whisking as you add the cream. It will thicken up as you go–spend at least five minutes on this. 
• Once all of the cream is added, turn the heat to low and add the freshly shredded cheese into the mixture. Let the heat of the roux begin to melt the cheese. Don't stir too much or it will get stringy. 
• Now it's time for washing, drying, and PEELING your potatoes before you slice them thinly with a mandolin (like this one).

(Unless you're incredibly patient and skilled with a knife, getting them thin enough with just a knife will be really tough.)

• Slice your potatoes into slices between ⅛ and ¼-inch thick. If they're not thin enough, they won't cook in time. 
• Add your sliced potatoes to a large bowl. Toss with additional salt and pepper, to taste.

• Grease an 8x8 oven-safe dish. 

• Add half of the sliced potatoes to the dish, laying as flat as possible. Top with half of the sauce. 
• Add the rest of the potatoes on top, keeping them as flat as possible. Top with the rest of the cheese sauce.

• Now cover the cheesy potato gratin with tin foil and place in the oven.
• Cook for 60 minutes, and remove from oven but keep oven on. If using parmesan, add it now. Return the potato gratin to the oven WITHOUT tin foil. Cook for another 15 minutes (75 minutes total).

Other vegetarian holiday recipes

One last thing before the specifics, here are some other vegetarian recipes for Christmas, Thanksgiving, Easter, etc. to check out:

• CHRISTMAS COOKIES: OATMEAL COOKIES W/ WHITE CHOCOLATE CHIPS & CRANBERRIES
• THE BEST VEGETARIAN CHRISTMAS APPETIZERS
• EASY CHEESY SCORED BAKED POTATOES

Cheesy Potato Gratin

📖 Recipe

There you have it! 

Happy holidays or happy regular dinner! No matter the occasion, I hope you just love this ultra cheesy potato gratin. 

XO,

– Chelsea

By the way, I also have a new page on my site with a bunch of helpful links. It has links to my social profiles, LTK, Amazon Storefront, etc. There's NO pressure to shop from any of these links. But if you're curious about the products I use, etc., that's where you'll find them. As always, I appreciate your support SO much!

Au Gratin Potatoes: FAQs

In case there's anything I didn't cover in the recipe, here are some common questions about this potato recipe in case you're asking the same thing.

What are au gratin potatoes?

Potatoes gratin are a classic French dish made with layers of thinly sliced potatoes, cream, and cheese, baked until the top is golden brown and crispy. They're a really popular side dish for family dinners, including special occasions like Christmas, Thanksgiving, and Easter. My family always eats them on Easter! 

What's the difference between au gratin potatoes and scalloped potatoes?

So, both dishes use sliced potatoes and are baked in a creamy sauce. However, au gratin potatoes have cheese (often grated on top), while scalloped potatoes traditionally do not.

Can I prepare au gratin potatoes in advance?

Yes, you can assemble the dish a day ahead, cover, and refrigerate. Before baking, let it sit at room temperature for about 30 minutes and then bake as directed.

What type of potatoes is best for au gratin?

Russet potatoes or Yukon gold potatoes are your best bet.

Can I add other ingredients to my cheesy potatoes? 

It's definitely worth a try! Common additions include onions, garlic, ham, bacon, and various herbs such as thyme or rosemary.

My sauce turned out too thin/runny. Why?

This can happen if:

• The potatoes released too much moisture during baking.
• The sauce wasn't thickened enough before adding to the potatoes.
• Too much milk or cream was used.

What's the ideal thickness for the potato slices?

As I mentioned before, around ⅛ to ¼ inch is a good thickness. Using a mandoline slicer can help achieve consistent, thin slices.

How do I get a crispy top layer?

Ensure you have a layer of grated cheese on top, and you can also sprinkle with breadcrumbs for extra crunch. If the dish is fully cooked but the top isn't browned enough, you can place it under the broiler for a couple of minutes, watching closely to prevent burning.

How long can I store leftovers?

I LOVE leftover potatoes au gratin. Leftovers can be stored in the refrigerator for three or four days. You can reheat them in the microwave but if you have the time, opt for the oven for the best results. 

What should I serve with au gratin potatoes?

They pair well with roasted meats, such as ham, beef, or chicken. They can also be complemented with green vegetables like green beans, asparagus, or a light salad.

Remember, the key to a great Au Gratin Potato dish lies in the balance of creamy sauce, tender potatoes, and a crispy, cheesy top layer. Adjusting ingredients to your preference can make the dish even more delightful!