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Potato & Tomato Gratin

September 17, 2010

“Let’s build a fire!” I said to B the other day, as I threw on a heavy sweatshirt. The tip of my nose was cold and I already had wool socks on my feet.

“But it’s not fire season yet — it’s only the beginning of September,” he replied.

“Well, September or not,” I countered, “it’s fifty degrees with rain and howling wind — perfect fire weather to me…besides, I’m freezing!” B looked at me, chuckled, and pulled on his boots to grab some firewood outside.

I don’t know why, but every September it takes me by surprise when crisp, crackly, cool Fall shows up on our doorstep, knocking loudly. And I don’t mind at all — I love pulling out my sweaters and earth-toned fall clothes, sleeping with a few extra blankets and waking up to crisp blue skies and fog-hugged hills.

My only regret — which is really a moot point since I’ve frozen bags upon bags of them in our chest freezer — is that blueberry season is over. However, no one is as sorry as our daughter A, who is a true blueberry monster:

September is sometimes a slightly discombobulating time at the farmer’s market for me. Often I’m pulling on a fleece jacket and debating whether or not to wear fingerless-gloves for a little extra warmth on my open-air shopping trip, but then the market stall shelves are brimming with produce that I associate more with the peak of summer — luscious ripe tomatoes, cucumbers, eggplants, peppers. I have to keep reminding myself that in our Zone 5 climate,  September and early October seem to really be our peak.

late summer/early fall potatoes, tomatoes & thyme

But this recent spate of cool weather is a nice excuse to turn on the oven again; my motivation to bake skyrockets and all I crave are warm roasted things, soups, casseroles, and this year, gratins.

sweet, toffee-colored caramelized onions

A recent addition to my cookbook collection is Sunday Supper at Lucques by Suzanne Goin, which — if you don’t already have it — I’m recommending to all my friends who love to cook. I’ve spent many a dreamy weekend afternoon while the baby sleeps thumbing through her seasonal menus and dreaming of how the dishes must taste. I made her fresh corn soup over the summer (oops – time came and went and that never made it to the blog), and top on my list to try when fall arrived was this potato and tomato gratin.

thinly sliced potatoes tossed with cream, salt and thyme

luscious, drippingly ripe tomatoes waiting to be tucked into the gratin

For this gratin, potatoes and tomatoes are thinly sliced and seasoned with cream and thyme, then tucked into layers with golden-brown caramelized onions.

layering, layering

make the top presentation pretty!

After a showering of basil over the top, the gratin is baked until the potatoes are tender and tomatoes exude their juices and melt into the dish. The entire dish is wonderfully seasoned and a pitch-perfect bridge from summer to fall.

A few recipe notes:

  • Goin is very precise with measurements for seasoning with salt and pepper throughout each recipe in her book. As someone who tries to accurately season (but sometimes can overseason things in my paranoia about making things underseasoned), I find this helpful.
  • It takes almost 3 hours start to finish when you factor in a 2+ hour bake time. Which, I think, makes it a great recipe for a weekend afternoon, but probably not a good weeknight side dish. The dish is marvelous, though, so don’t let the 2-hour bake time deter you. Just don’t plan to make this on a Thursday night like I initially did. 🙂


Potato Tomato Gratin

From Sunday Suppers at Lucques by Suzanne Goin

5 tablespoons extra-virgin olive oil
6 cups thinly sliced onions (about 1 1/2 pounds)
1 tablespoon thyme leaves, divided
1 tablespoon unsalted butter
1 1/4 pound Yukon Gold potatoes, peeled (note: I did not peel mine)
1/2 cup heavy cream
2 1/4 pound ripe tomatoes (I used a mix of red and green tomatoes)
1/4 cup sliced basil
kosher salt and freshly ground black pepper


Heat a large saute pan or Dutch oven over high heat until hot, then add 3 tablespoons olive oil, the onions, 1 teaspoon thyme, 1 teaspoon salt, and some pepper. Cook for 6 minutes, stirring often, then turn down the heat to medium and add the butter. Cook an additional 10-15 minutes, scraping with a spoon or spatula until the onions start to caramelize. Turn the heat down to low and continue cooking until the onions are a deep golden brown, another 5-10 minutes. Turn the heat off and set aside.

Preheat the oven to 350 degrees F.

Thinly slice the potatoes (using a mandoline or a sharp chef’s knife) into 1/8-inch-thick rounds. Toss them in a bowl with the cream, 1 teaspoon thyme, 1 teaspoon salt, and some freshly ground black pepper.

Slice the tomatoes into 1/4-inch thick slices, arrange them on a plate and season with 1 teaspoon salt and some pepper.

To layer the gratin, first spread half the caramelized onions in an even layer in a 9×9 inch gratin or baking dish. Top the onions with one layer of alternating potatoes and tomatoes (using about half of each), then drizzle with 2 tablespoons cream (from the potato bowl) and 1 tablespoon olive oil. Season with 1/4 teaspoon salt, a healthy pinch of black pepper, 1/2 teaspoon thyme and half the basil.

Repeat the layers, making the top potato/tomato layer pretty since this is the top presentation layer of the gratin. Pour the remaining cream (from the potato bowl) and remaining tablespoon olive oil over the gratin and season with 1/4 salt, a pinch of pepper, the remaining 1/4 teaspoon thyme and the remaining basil. Press all the vegetables down with your fingers; the cream will come up through the layers and coat the vegetables evenly.

Cover the baking dish tightly with aluminum foil and bake for 1 1/2 to 2 hours, until the potatoes are tender when pierced. Turn the oven temperature up to 450 degrees F, uncover the gratin, and bake an additional 25-30 minutes until the top is bubbly and golden brown. Let cool slightly before serving.

16 Comments leave one →
  1. geraldine pease permalink
    September 17, 2010 6:42 pm

    I love your website!!! I’m sending it to people I know. Wonderful images etc. THANK YOU!!! gp

  2. Maggie permalink
    September 17, 2010 7:32 pm

    Looks delicious – I’m going to have to try this! Such a cute picture of little A 🙂

  3. September 17, 2010 11:55 pm

    That sounds delicious! And your daughter is adorable. My son feels the same way about blueberries. And blackberries. And all berries. It’s going to be a rough winter.

  4. September 18, 2010 1:25 am

    What a perfect way to slide summer into fall! And that is an awfully cute little blueberry eater you got there 🙂

  5. September 18, 2010 5:11 pm

    We built a fire on this morning and evening earlier this week, it’s been rather chilly but I LOVE it! This gratin is perfect, as I have some tomatoes left over from my week of preserving them in different ways. Adding this to the menu this week 🙂 thanks!!

  6. September 19, 2010 9:45 am

    That looks really delicious!!! Thank you!

  7. September 19, 2010 3:34 pm

    Ooh, this looks perfect for the cooler evenings we’ve been having! Love it!

  8. September 22, 2010 6:13 pm

    Oh, I think we are going to have lots of farm share members firing up their ovens this weekend as the tomatoes are going strong and we’ve just brought in loads of potatoes. Oh, how good it sounds. Hopefully I’ll find the time to try this recipe. And as always, your blog is my first go to for inspiration for my members. Thank you!
    Laura Olsen
    Green Mountain Girls Farm

  9. September 23, 2010 1:31 pm

    Amy- I made this earlier in the week and it was delicious. Even more impressive: I had to use my toaster oven (!) because we are waiting to get a gas line installed for our new stove. Regardless of the challenge, it turned out beautifully and was simple to assemble. Thanks for sharing such a great recipe.

  10. Sherry permalink
    October 2, 2010 6:00 pm

    This was absolutely fabulous Amy! It was just as good the 2nd night, and a great way to use those tomatoes that are still coming …. I always look to your blog for delicious and interesting dishes, you never disappoint!

  11. Virginia permalink
    October 5, 2010 5:43 pm

    I was inspired by your photos to make this dish. However, I don’t think it came out anything like yours. It was extremely juicy- it practically made a sauce. I don’t think the tomatoes were over ripe. If I make it again I think I will seed the tomatoes and possibly peel the potatoes. I really couldn’t taste the delicious onions due to the juice. I baked it for 2 1/2 hours. Has anyone else had the same problem?

    I do love your blog and have cooked many of your recipes. My favorite for taste and quickness is Garlicky Greens.
    Thanks for the blog,

  12. October 8, 2010 11:46 am

    She may be a blueberry monster, but she’s a very CUTE blueberry monster! 🙂

  13. October 8, 2010 8:23 pm

    Wow! A very healthy meal, love to try it! Happy Weekend!

  14. Célia permalink
    October 13, 2010 11:46 am

    Very good recipe! My fiancé made it for me, and we both found it very tasty!

  15. January 24, 2011 3:37 pm

    Look at those gorgeous tomatoes! Gorgeous. Ah last September…

  16. August 21, 2011 4:24 pm

    YUM – I currently have lots of tomatoes & potatoes and look forward to cooking this up next weekend (once I finish the pile of tomatoes on the counter and as another pile is overflowing)

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