Brown Butter Potatoes au Gratin with Gruyere and Caramelized Onions

Oh man. I just started going to spin class. WHAT did I get myself into. Everything from my belly button down is just sore. I get out of class and from 54th to 68th street and my cheeks are bulbous and puffy red like a chipmunk with hives.

Clearly I am not very attractive when I exercise. But it feels great knowing the strength of your body and what it is capable of. And lately when I’ve come home from my 45-minute intensive class I’ve had myself to thank for making this yummy dishes and saving lots and lots of leftovers to fill my guilty post-workout carb cravings.


As with pretty much ALL of my dishes, let’s start with the herbs. Other than the Simon & Garfunkel song, there are other reasons why I fell in love with rosemary and thyme. I mean would it be awful if I named my two daughters after them? “Thyme dear, could you help your old mother open up this pickle jar?” I don’t know I think it works.

But other than the salty taste that most gratins have, I love adding these two herbs because I feel it gives the potatoes and cheese and really wonderful aroma and more of a distinctive taste.

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Caramelized onions can never look good on camera. But you know as much as I do that they are DELICIOUS. Who ever knew slimy slug-like food could make me salivate so. I’m sorry I didn’t mean to put that image in your mind. Let’s get back to the delicious thoughts.

Which are THESE onions. I really don’t mind putting in the extra time to caramelize them. You’ll be thanking yourself in the end when you take that first cheesy bite.


For this dish, I managed to use the same saucepan to make the onions, the cheese sauce and to bake the whole darn thing when it was all combined. I felt that was an accomplishment. And this is the only place I can brag about it.

Thank you interwebs.


Brown Butter Potatoes au Gratin with Gruyere and
Caramelized Onions

Serves 4-6

2 onions, sliced
2 tbsp olive oil
4 russet potatoes, thinly sliced
5 tbsp unsalted butter
3 tbsp all-purpose flour
1 tsp sea salt
2 cups whole milk
2 cloves garlic, minced
2 tbsp rosemary, finely chopped
2 tbsp thyme, finely chopped
2 cups shredded gruyere

Preheat oven to 400ºF. Butter a casserole dish or an oven-proof sauté pan, and set aside.

Heat the oil in a large skillet over high heat. Add sliced onions, constantly stirring with spatula. The onions should start to brown, but without burning. Reduce heat to medium and continue stirring as onions brown even more without burning. Add a little bit of water if they start to stick. Once they’ve gotten very brown and soft (after about 45 minutes) remove from heat. Put onions in a small bowl, and set aside.

Melt butter over medium heat in a saucepan. Keep an eye on the butter and stir occasionally. Soon the butter will start to brown fairly quickly. Once the butter solids become an amber color and butter smells slightly nutty, immediately add in flour and salt and mix constantly for 1 minute. Add in milk as well as garlic, rosemary and thyme. Cook until mixture has thickened. Gradually add in gruyere until cheese has melted.

Layer ½ of potatoes topped with caramelized onions in baking dish. Season with salt and pepper and extra chopped rosemary and thyme. Add ½ of the cheese sauce on the layered potatoes and onions. Layer the rest of the potatoes on top and the remaining sauce over it. Make sure it covers all the potatoes on top. Season with salt and pepper and add remaining rosemary and thyme stalks.

Bake for 1 ½ hours in the preheated oven and serve immediately!

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38 thoughts on “Brown Butter Potatoes au Gratin with Gruyere and Caramelized Onions

  1. OMG this looks amazing!!! It’s like a gourmet version of potatoes gratin which can be kind of boring. Rosemary, gruyere, and caramelized onions- so not boring 🙂 cannot wait to try this. And great photos!

  2. Man, those potatoes look so yummy I might start drooling like the dogs do when I’m eating something they like. Pinning this one to try in the cooler months.

  3. Hi there – Kelli from Yum Goggle – thank you so much for submitting such a lovely recipe to our food site. We are now following you on all available social media and hope you will do the same. We will be promoting your recipes on up to 12 social media platforms available to us and will tag you on all that you follow us/we follow you on.

    We hope you will continue to submit posts – we are blogger friendly so if you have questions or concerns please email us. Also, when the submission page asks for the name of your blog, please just put the name – no need to add http://www or .com – it’s completely linkable and when you do put that in, I have to take it so it will work correctly on the gallery side.


  4. This looks AMAZING, but the addition of caramelized onions makes me know it has to be even better than I think. I’d love to have some in front of me right now! Thank you so much for sharing with us at Delicious Dish Tuesday! We’d love for you to share a link back to one of the hosts so your readers know where to find (and share) more amazing recipes like this one! Can’t wait to see what you bring us next week!!!!! Happy cooking! 🙂

  5. Growing up my grandmother (who was French) used to make a potatoes au gratin similar to this. While she didn’t use Rosemary, the star of the show was the Gruyere. This looks divine. Thanks for sharing. Emilie

  6. As I was reading this post, my boyfriend walked up behind me and said, “Ooh what’s that?! Will you make me that? That’s a nice website. You should keep reading that…”. Yup. That pretty much sums it up. I’m drooling.

  7. I made this tonight! Sooo fabulous!! Love the different flavor imposed by the rosemary. The caramelized onions made this potato dish taste and feel like a dessert we were sneaking before finishing dinner! Served with filet mignon and steamed broccoli. I substituted coconut milk for the whole milk, but it worked fine, and the “sauce gruyere” was magnifique! Thanks for posting this awesome recipe. Best gratin I’ve ever prepared. 😊

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