Easy Potatoes Au Gratin

By Rena |

This Potato au Gratin recipe is easy to make, creamy, and full of flavor. It makes for a cheesy holiday potato side dish recipe that will be the perfect addition to the dinner table.

top view potato au gratin in a white dish

Make this homemade au gratin potatoes all year round, a potato side dish that pairs so well with all your main courses especially all your sautéed and grilled protein of choice. Often times referred to as scalloped potatoes, the flavor of this au gratin is top-notch with the addition of whole-grain mustard. It gives it that extra boost in the flavor department. The potatoes are prepared in a creamy cheesy sauce and baked to perfection. This cheesy au gratin recipe will be your go-to holiday potato side dish recipe every year and you would want to make it all year round.

Why you will love this potato side dish recipe

  • Delicious and comforting: The flavor of this potato au gratin is so good, there won’t be any leftovers.
  • Easy to make: You can partially prepare some of the steps ahead and store in the fridge to bake the next day. The steps and simple and easy to follow.
  • Healthy: Made with clean and healthy ingredients. Don’t like gruyere? you may substitute for light cheddar.
top view close up image of au grain in a white dish

Ingredients you will need to make this au gratin

potatoes 

Kosher salt and freshly ground black pepper

olive oil

medium yellow onion

garlic cloves

whole grain mustard

gluten free flour or cornstarch 

almond milk

freshly grated nutmeg

Gruyère cheese 

Fresh thyme

ingredients for potato au gratin

How to make this au gratin potatoes

  • First, preheat the oven to 400F and spray a baking dish with cooking oil spray or olive oil. 
  • Then, add sliced potatoes and season with salt and pepper. Drizzle 2 tbsp oil and toss well to coat. Place in the preheated oven and bake for 15 minutes, or until potatoes begin to soften and the sauce is ready.
  • Meanwhile, heat a rimmed pan over medium heat and drizzle with 1 tbsp oil. Sauté the onion and garlic for 2-3 minutes, or until it softens.
  • Stir in the mustard and flour. Slowly pour the milk and whisk until sauce is thickened and smooth, 2-3 minutes. Season with salt, pepper, and nutmeg.
  • Remove the potatoes from the oven and pour over the sauce, stirring gently to mostly cover and coat.
  • Top with shredded cheese. (You can now cool and refrigerate the dish for make-ahead.)
  • Return to the oven and bake for 60 minutes, or until potatoes are super tender, bubbly, and golden-brown on top. (Cooking time may vary depending on the size of the thickness of your potato slices and your oven.)
  • Garnish with fresh thyme before serving.
top view au gratin in a white dish

Tips and substitutes

Milk: we used almond milk, but you may use any other milk of choice.

Mustard: whole grain mustard was used but you may use dijon mustard

Cheese: If you don’t like gruyere or want to use another cheese, consider using a mix of sharp cheddar and parmesan, or gouda.

Potatoes: consider using Yukon gold potatoes 

Flour: Any flour would work for this recipe. Feel free to use cornstarch too. We love to use Whole wheat as well.

Bake time: Don’t rush them, they need a good one hour in the oven depending on your oven

spoon in au gratin, top view

FAQ’s

Do you peel au gratin potatoes?

Technically, you don’t have to peel the potatoes. You can scrub them very clean and slice them with the peel. But, we prefer peeling the potatoes for the au gratin as you can see in our recipe. It all comes down to a personal preference.

Can you make au gratin potatoes ahead of time and reheat them?

Yes. You can fully cook the au gratin, store, and reheat later as a make ahead option to save time. We recommend not adding all the cheese so you may add the rest when its time to reheat in the oven. Also, consider cooking it half way like we noted in our recipe to save time the day of.

Can I slice potatoes the day before for au gratin?

Yes. You may clean and slice your potatoes the day before. Once you have the sliced potatoes, place in a container filled with cold water and tightly close it. Place in the fridge until you are ready for them.

How to store au gratin potatoes?

Place leftover potatoes au gratin in a tightly sealed container and store in the fridge for 3-4 days. You may freeze for up to 2 months,

top view of white dish with baked potatoes au gratin

What goes well with au gratin potatoes

Here are some ideas of what you can have with au gratin potatoes.

Other side dish recipes to check out

side shot of baked au gratin in white dish

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top view potato au gratin in a white dish

Easy Potatoes Au Gratin

Tender sliced potatoes baked to perfect with a creamy sauce made with milk, cheese, garlic, mustard, and onions.
5 from 1 vote
Print Pin Rate
Course: Side Dish
Cuisine: American, French
Prep Time: 15 minutes
Cook Time: 1 hour 20 minutes
Total Time: 1 hour 35 minutes
Servings: 8
Calories: 127kcal
Author: Rena

Ingredients

  • 2 lb potatoes peeled and thinly sliced
  • Kosher salt and freshly ground black pepper to taste
  • 3 tbsp olive oil divided
  • 1 medium yellow onion thinly sliced
  • 3 garlic cloves minced
  • 1 tbsp wholegrain mustard
  • 3 tbsp gluten-free flour or cornstarch
  • 2 1/2 cups almond milk
  • 1 tsp freshly grated nutmeg or to your taste
  • ¾ cup grated Gruyère cheese
  • Fresh thyme to garnish

Instructions

  • Preheat the oven to 400F and spray a baking dish with cooking oil spray or olive oil.
  • Add sliced potatoes and season with salt and pepper. Drizzle 2 tbsp oil and toss well to coat. Place in the preheated oven and bake for 15 minutes, or until potatoes begin to soften and the sauce is ready.
  • Meanwhile, heat a rimmed pan over medium heat and drizzle with 1 tbsp oil. Sauté the onion and garlic for 2-3 minutes, or until it softens.
  • Stir in the mustard and flour. Slowly pour the milk and whisk until sauce is thickened and smooth, 2-3 minutes.
  • Season with salt, pepper, and nutmeg.
  • Remove the potatoes from the oven and pour over the sauce, stirring gently to mostly cover and coat.
  • Top with shredded cheese. (You can now cool and refrigerate the dish for make-ahead.)
  • Return to the oven and bake for 60 minutes, or until potatoes are super tender, bubbly, and golden-brown on top. (Cooking time may vary depending on the size of the thickness of your potato slices.)
  • Garnish with fresh thyme before serving.

Notes

Milk: we used almond milk, but you may use any other milk of choice.
Mustard: whole grain mustard was used but you may use dijon mustard
Cheese: If you don’t like gruyere or want to use another cheese, consider using a mix of sharp cheddar and parmesan, or gouda.
Potatoes: consider using Yukon gold potatoes 
Flour: Any flour would work for this recipe. Feel free to use cornstarch too. We love to use Whole wheat as well.
Bake time: Don’t rush them, they need a good one hour in the oven depending on your oven

Nutrition

Calories: 127kcal | Carbohydrates: 4g | Protein: 5g | Fat: 10g | Saturated Fat: 3g | Cholesterol: 14mg | Sodium: 165mg | Potassium: 35mg | Fiber: 1g | Sugar: 1g | Vitamin A: 117IU | Vitamin C: 1mg | Calcium: 226mg | Iron: 1mg
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