Rich Potato Gratin

Potato gratin has this way of making any dinner feel special. I remember my mom making it for Sunday dinners when I was growing up, and now I find myself doing the same thing for my own family. There’s something about those creamy, cheesy layers that just hits different than regular mashed potatoes.

The best part? It’s actually pretty simple to make, even though it looks fancy on the table. You slice, you layer, you pour some cream over it, and the oven does most of the work. I love that I can prep it earlier in the day and just pop it in when we’re getting close to dinner time.

Whether you’re making it for a holiday meal or just want to dress up a weeknight dinner, this potato gratin recipe is going to become one of those dishes people ask you to bring to every gathering. Trust me on this one.

What Kind of Potatoes Should I Use?

For potato gratin, you’ll want to stick with starchy potatoes like Russets or Yukon Golds since they hold their shape well and create that creamy texture we’re after. Russets are my go-to choice because they have a higher starch content, which helps thicken the cream sauce naturally as it bakes. Yukon Golds work great too and give you a slightly buttery flavor that pairs nicely with the cheese. Avoid waxy potatoes like red potatoes or fingerlings for this recipe, as they won’t break down enough to create that perfect creamy consistency. When slicing your potatoes, aim for about 1/8-inch thick slices – a mandoline slicer makes this job much easier and ensures even cooking.

Options for Substitutions

This creamy potato gratin is pretty forgiving when it comes to swaps, so here’s what you can change up:

• Gruyere cheese: Gruyere gives the best flavor, but if you can’t find it, try Swiss cheese, sharp cheddar, or even a mix of parmesan and mozzarella. Just keep the total amount the same.
• Milk or heavy cream: You can use either milk or heavy cream depending on how rich you want it. Half-and-half works great as a middle ground. For dairy-free, try unsweetened oat milk or cashew cream.
• Potatoes: Russet potatoes are classic for gratin, but Yukon golds work well too and hold their shape nicely. Avoid waxy potatoes like red potatoes as they won’t get as creamy.
• Butter: You can substitute with olive oil or vegan butter if needed, though butter gives the best flavor for the roux.
• Fresh thyme: Dried thyme works fine – just use half the amount. You could also try rosemary or sage, but use them sparingly as they’re stronger.
• Flour: For gluten-free, use a 1:1 gluten-free flour blend or cornstarch (use 2 tablespoons instead of 3).

Watch Out for These Mistakes While Baking

The biggest mistake when making potato gratin is slicing your potatoes too thick, which prevents them from cooking evenly – aim for slices about 1/8 inch thick using a mandoline or sharp knife for consistent results.

Another common error is not seasoning each layer as you build the casserole, so make sure to sprinkle salt and pepper between every few layers of potatoes rather than just on top.

To avoid a lumpy sauce, whisk your flour into the butter mixture thoroughly before slowly adding the milk, and don’t rush this step or you’ll end up with clumps that won’t smooth out.

Finally, cover your gratin with foil for the first hour of baking to prevent the top from browning too quickly before the potatoes are tender, then remove the foil for the last 15-20 minutes to get that golden, bubbly finish.

What to Serve With Potato Gratin?

Potato gratin is the perfect side dish for so many meals, but it really shines alongside roasted meats like beef, pork, or chicken. The creamy, cheesy potatoes pair beautifully with something simple like roasted chicken thighs or a nice steak, where the rich gratin balances out the protein perfectly. I also love serving it with a fresh green salad dressed with lemon vinaigrette to cut through all that delicious cream and cheese. For holidays or special dinners, try it with roasted vegetables like Brussels sprouts or green beans to round out the meal.

Storage Instructions

Refrigerate: Leftover potato gratin keeps really well in the fridge for up to 4 days. Just cover it tightly with foil or transfer portions to airtight containers. The creamy sauce might look a little separated when cold, but don’t worry – it comes back together beautifully when you reheat it.

Freeze: You can freeze potato gratin for up to 3 months, though the texture will be a bit different after thawing. I like to cut it into individual portions first, then wrap each piece in plastic wrap and store in freezer bags. It’s great for having a comforting side dish ready to go!

Warm Up: To reheat, cover with foil and bake at 350°F for about 20-30 minutes until heated through. If you’re warming up a single serving, the microwave works fine too – just use medium power and stir halfway through. Add a splash of milk if it seems too thick.

Preparation Time	20-30 minutes
Cooking Time	45-60 minutes
Total Time	65-90 minutes
Level of Difficulty	Medium

Estimated Nutrition

Estimated nutrition for the whole recipe (without optional ingredients):

• Calories: 2600-2900
• Protein: 60-70 g
• Fat: 115-130 g
• Carbohydrates: 340-370 g

Ingredients

For the cheese sauce:

• 3 tbsp flour (all-purpose or gluten-free)
• 1 1/2 cups milk (or heavy cream for extra richness)
• 1/2 cup shredded gruyere cheese (freshly grated if possible)
• 1 pinch ground nutmeg (optional but recommended for depth)
• 1 tsp fresh thyme, chopped (or 1/2 tsp dried)
• 3 tbsp butter (I use Kerrygold unsalted butter for richness)
• 1 small onion, minced (about 1/4-inch pieces)
• 1 garlic clove, grated (freshly minced preferred)
• Salt and black pepper, to taste

For the potato base:

• 1 cup shredded gruyere cheese (freshly grated for best melting)
• 4 lb potatoes, sliced thin (about 1/8-inch thickness)

Step 1: Prepare Mise en Place and Preheat Oven

• 4 lb potatoes
• 1 small onion, minced
• 1 garlic clove, grated
• 1 tsp fresh thyme, chopped
• 1 1/2 cups shredded gruyere cheese

Preheat your oven to 350°F.

While it heats, slice the potatoes into thin 1/8-inch rounds—I recommend using a mandoline or the slicing blade on a box grater for consistency, which ensures even cooking.

Mince the onion into small pieces, grate the garlic clove, chop the fresh thyme, and grate both portions of gruyere cheese.

Having everything prepped and ready will let you focus on building the sauce without interruption.

Step 2: Build the Béchamel Base with Aromatics

• 3 tbsp butter
• 1 small onion, minced
• 1 garlic clove, grated
• 1 tsp fresh thyme, chopped

Melt the butter over medium heat in a saucepan.

Add the minced onion, grated garlic, and thyme, sautéing gently for 3-5 minutes until the onion softens and becomes translucent—this develops a subtle flavor foundation without browning.

The aromatics infuse the butter, creating a more complex and layered sauce than if you simply made a plain béchamel.

Step 3: Make the Cream Sauce

• 3 tbsp flour
• 1 1/2 cups milk
• 1/2 cup shredded gruyere cheese
• 1 pinch ground nutmeg
• Salt and black pepper, to taste

Sprinkle the flour over the aromatic mixture and cook for 1 minute, stirring constantly to create a roux—this cooks out the raw flour taste.

Pour in the milk slowly while whisking vigorously to prevent lumps, then continue whisking for 1-2 minutes until the sauce thickens to a consistency that coats the back of a spoon.

Remove from heat and stir in the 1/2 cup gruyere cheese, ground nutmeg, salt, and pepper until the cheese melts completely and the sauce is smooth and creamy.

Step 4: Layer the Potatoes with Sauce

• cream sauce from Step 3
• 4 lb potatoes, sliced thin

Pour a thin layer of the cream sauce from Step 3 onto the bottom of a buttered baking dish—this prevents the potatoes from sticking and ensures every bite has creamy richness.

Arrange half the sliced potatoes in an overlapping pattern over the sauce, then pour roughly half of the remaining sauce over them.

Add the remaining potatoes in another overlapping layer, then pour the rest of the sauce over the top, making sure to fill in any gaps so the gratin cooks evenly.

Step 5: Bake and Finish the Gratin

• 1 cup shredded gruyere cheese

Sprinkle the remaining 1 cup of grated gruyere cheese evenly over the top of the potato layers.

Bake at 350°F for 45-60 minutes, until the potatoes are tender when pierced with a knife and the top is light golden brown.

If you want a deeper, more caramelized crust, turn on the broiler for the final 2-3 minutes, watching carefully to prevent burning.

Remove from the oven and let the gratin rest for 10 minutes before serving—this allows the layers to set slightly, making it easier to portion and ensuring a creamier interior.