This Spinach Potatoes Au Gratin with Gruyère is well worth every minute it takes to prepare. The flavors are deep, the textures are smooth, and the overall takeaway is one of over-the-top, comforting deliciousness, and it never disappoints!
Talk about vegetarian comfort food!
This dish is delicious, packed with flavor, and super satisfying, yet not too rich or heavy.
I love the layering process involved in creating this incredible gratin. It's a bit of a project to make it, but I think it's worth it. And, you can make it a few days ahead!
First, what is Potatoes Au Gratin?
Au gratin (or gratin) generally refers to a dish with a golden brown top. In this potato and spinach gratin, there's a mixture of half-and-half, herbs and spices that coat thinly sliced potatoes, layered with spinach, topped with grated onion and Gruyère, all beautifully browned in the oven.
The word gratin also refers to an oval-shaped baking dish -- which is the way you'll typically see most au gratins presented. Though mine is rectangular. 😉
Ingredient Notes
- russet potatoes - Their starch helps the layers hold together and gives the gratin its creamy texture. Slice them as thinly as possible.
- half-and-half - It's simmered with the garlic and spices until it's reduced, then used to soak the potatoes and fill the gratin.
- Gruyère cheese - It melts perfectly and has a subtly sweet, nut-like flavor. Substitution: Jarlsberg is a great alternative.
- fresh spinach - The fresh spinach adds pop of color (and nutrition. ;-))
- onion - Grated (or sliced super thinly), with the excess liquid squeezed out.
- garlic, dried thyme, nutmeg and allspice - These warm, aromatic flavors infuse the half-and-half, and then that mixture imparts its flavor into the potato slices.
- unsalted butter, salt and pepper
How to Assemble
I've laid out the steps for assembly very carefully for you because much of the success of this gratin is in the layering process. (You'll find the complete instructions below in the recipe card.)
- Add two layers of potato slices that have been soaking in the half-and-half-spice-herb mixture to a 9 x 13 x 3-inch casserole dish. Top them with grated onion and Gruyère, followed by fresh spinach.
- Then these three steps are repeated and followed by more potatoes, onions and cheese. It will literally be almost overflowing.
- To compress everything, weigh it down for about an hour with another pan and heavy cans, compacting all of the ingredients together.
Variations
- Cheese. Instead of Gruyère, try Emmental or Jarlsberg.
- Greens. Instead of spinach, try kale (I would not use curly) or chard.
Recipe Tips
- This is a recipe where it's especially important to read through all the steps before you get started.
- The thinner you slice the potatoes, the better. If they're super thin, they become almost like flat pasta. Using a mandoline slicer is ideal.
Can you make this gratin ahead of time?
Yes, you can! This is a dish that only gets better with time. You can make the entire thing up to 3 days ahead of time. After it comes out of the oven, let it cool completely, wrap it tightly and keep it refrigerated. Reheat it, covered, in a 375°F oven for about 30 minutes.
Serving Suggestions
- For a vegetarian meal, I serve the potato and spinach gratin as the main course with a vegetable side dish. It's fantastic with oven-charred broccoli, pan-seared oyster mushrooms, and glazed carrots.
- And if keeping it vegetarian isn't important for you, the gratin becomes the side dish (it's wonderful for Thanksgiving and holiday dinners), and you can serve it with chicken or meat. It's especially good with Mediterranean Flank Steak, Lavender-Grilled Ribeye, and whole roasted chicken with lemon.
- However you serve it, a salad is always a lovely addition, and frankly, I think it can also totally stand alone.
Must-Try Potato Gratin-Like Recipes
As I said, this recipe takes time. If you enjoy the cooking process, being in the kitchen and delicious food, this is for you.
Enjoy!
Spinach Potatoes Au Gratin with Gruyère Recipe
Equipment
- 9 x 13 x 3-inch baking dish ideally 2, for weighing it down
Ingredients
- 1 large onion about 1⅛ pounds
- 5 cups half-and-half
- 1 tablespoon garlic minced
- 1½ teaspoons dried thyme
- ⅛ teaspoon nutmeg
- ¼ teaspoon allspice
- 1½ teaspoons salt
- ½ teaspoon freshly ground black pepper
- 5 pounds Idaho russet potatoes
- 3 cups fresh spinach leaves tightly packed, washed and dried
- 3 cups Gruyère cheese grated
- 2 tablespoons unsalted butter melted
Instructions
- Grate the onion. Peel the onion and cut it in half or quarters to grate it. A food processor with the grater attachment is easiest. Alternately, you can slice the onion super thinly. Add the grated onion to a strainer over a bowl and set aside.
- Make the half-and-half mixture. In a large sauce pot, combine the half-and-half with the garlic, thyme, nutmeg and allspice. Bring to a boil and then immediately reduce to a low simmer. Simmer until the mixture has reduced by about ¼, about 25 minutes. Remove from the stove, strain, and add the salt and pepper. Let it cool until it's warm, or to room temperature.
- Slice the potatoes and add them to the half-and-half mixture. Peel the potatoes and slice them as thinly as possible, adding them to the half-and-half mixture as you go. Make sure the slices aren't stuck together and that all of them become well coated with the mixture. (I use the slicer attachment on my food processor for this, but you can also use a Chef's knife or a mandoline.) Let the potato slices soak for about 30 minutes.
Assembly
- Layer. Brush a bit of the melted butter on the bottom and sides of an approximately 9 x 13 x 3-inch baking dish.Without wiping them off, add two even layers of the potato slices from the half-and-half mixture. You should not be able to see the bottom of the dish when you're done. Sprinkle lightly with salt and pepper. DO NOT THROW OUT THE HALF-AND-HALF MIXTURE! Squeeze any remaining liquid out of the onions and sprinkle about ⅓ of them evenly on the potatoes, followed by 1 cup of the Gruyère cheese. Add ½ of the spinach leaves. (They will not lay flat.)Repeat the above layering steps.Add another two layers of the potatoes. Do not worry if nothing is laying flat -- at this point, it will look high and rounded, and likely sitting above the edges of the dish. This is how it should be. Set aside the remaining melted butter, onions, cheese, and all of the half-and-half mixture.
- Compress. Cover the dish tightly with plastic wrap and put a second dish directly on top -- ideally one that's the same size so the bottom of the top dish is pressing directly onto the plastic-covered, top layer of potatoes. Everything will flatten out at this point. Now weigh down the top dish -- canned food is perfect. Fill the top pan with as many cans as will fit, and place this entire set-up in the refrigerator for 1 hour. While it's in the refrigerator, preheat the oven to 375°F.Weighing down the gratin is a way to get any excess liquid out of the potatoes. Remove the gratin from the refrigerator and take off the weights and top dish. Keeping it covered with the plastic, holding it over the sink, slowly pour out any excess liquid from one of the corners. You can hold the palm of one hand down on the top surface of the gratin (on the plastic), to be sure nothing slides around.Remove the plastic wrap completely and sprinkle the top with a bit more salt and pepper, and then the remaining onions and cheese.
- Add remaining ingredients. Stir the saved half-and-half mixture to ensure the garlic and herbs are not sitting at the bottom. Pour it into the gratin until it goes about ¾ the way up the sides (it will be about 1½ cups or so). Use a dull knife to move the potatoes a tiny bit along the edges, to be sure it seeps through to the bottom.
- Bake and cool. Drizzle the top with the remaining melted butter, place the pan on a baking sheet and then place it in the preheated 375°F oven. Bake for 50 minutes. Then cover the pan loosely with foil and continue to bake for another 25 minutes.If the top of the gratin hasn't become golden brown, place it under the broiler briefly, about 30 seconds. Let the gratin sit for at least 45 minutes before cutting and serving.
If you've made this, a star rating would mean so much and helps other readers too! If you haven't made it yet, please skip the stars and just leave a comment. I'd still love to hear from you.
Natalie Ellis
I love the way it is full of potatoes and creaminess, but it isn’t too rich or heavy.
So I guess I have to give it a try to confirm what you said xD
valentina
I hope you do Natalie! 😀 Enjoy!