I used one of my blessedly cool afternoons to try out a recipe based on this one from the excellent blog 101 Cookbooks. It’s a gratin of tomatoes and potatoes with caramelized onions and flavorful spices. I’ve had the ingredients to makes this dish, or at least ingredients I thought would probably work, for some time. While the inspiration recipe (which you should check out…the photos are better) called for sliced tomatoes and Yukon gold potatoes, I happened to have lots of cherry tomatoes (some from the CSA and some from my patio garden), and purple potatoes (yes, they’re purple on the inside, too.)
I also had plenty of onions that had overstayed their welcome to use in the caramelized onion layer. I’m probably the last person who should be writing instructions on making caramelized onions. If you were to ask me, I would probably say, “I dunno, just cook them until they get all brown and soft.” Really, I think the key is to cook the onions low and slow and allow for different onions to perform differently based on their moisture and sugar content. Yellow onions seem to make the nicest brown and sweet caramelized onions. I cover the pan for the longest portion of the onion-cooking process so they sort of stew in their own juices, and then, when they look like they’re almost done, I remove the lid and let any remaining liquids boil away allowing the onions to get a little browner and just a little bit sticky. It’s pretty simple, but does take some time. That time, however, is totally worth it. A dish like this one is significantly enhanced by caramelized onions.
It is also enhanced by fresh ingredients and well-chosen spices. I used cumin and coriander to pep up my gratin, along with some slow-burning hot red pepper flakes. All of those flavors worked and played well with the sweet-tart cherry tomatoes and earthy potatoes. Since I flavored the cream with the spices and the cream was slurped up by everything in the dish, there was a good balance of seasoning throughout.
I’m more excited about this recipe than I have been about any new recipes for some time, and I don’t think it’s just because I’m excited about the break in the hot weather that allowed it to be made and enjoyed in more comfort. The juicy tomatoes lend some of their perky acidity to the cream and potatoes, and the caramelized onions add a brilliant sweetness. The smoky spices balance the sweetness and the potatoes, which are also pretty in their exotic purpleness, ground everything and hold it all together. I may just start making this dish even when it’s too hot for the oven. Well, let’s not get too crazy just yet.
Spicy Potato and Tomato Gratin with Caramelized Onions
Based on a recipe from the blog 101 Cookbooks
2 teaspoons ground cumin
2 teaspoons ground coriander seeds
½ teaspoon crushed red pepper flakes
3 tablespoons olive oil, divided
1 pound yellow or white onions, thinly sliced
1½ teaspoon coarse (kosher) salt, divided
¾ pounds potatoes, thinly sliced (about 1/8 inch thick)
½ cup heavy cream
1 pound cherry tomatoes, cut in half
1 cup whole wheat breadcrumbs, preferably fresh
1. Combine the cumin, coriander and red pepper flakes in a small bowl. Set aside.
2. To cook the onions, heat 2 tablespoons of the olive oil in a large skillet with a lid over medium heat. Add the onions and ½ teaspoon salt. Cook, stirring often for about 5 minutes or until beginning to brown. Cover, reduce heat to low, and cook about 20 minutes or until the onions are very soft and very brown. (You can prepare the remaining ingredients while this is going on.) Lift the lid to stir occasionally.
3. Remove the lid and continue cooking until most of the liquid has evaporated, 5 to 10 minutes, stirring occasionally. Remove from the heat. Stir in half of the cumin mixture and set aside.
4. Preheat the oven to 350 F. In a medium sized bowl, combine the sliced potatoes, cream, remaining 1 teaspoon salt and remaining cumin mixture. Stir to coat the potatoes.
5. Spread half of the cooked onions in the bottom of a 2 quart (or similar size) casserole dish. Layer half of the potatoes over the onions (your clean hands are the best tool for this job). Layer half of the tomatoes over the potatoes.
6. Scoop up a few tablespoons of the cream in the potato mixture and pour it over the tomato layer. Spread the remaining onions over the tomato layer, then the remaining potatoes over the onions. Press down on the potatoes to squash the layers together. Finish with a layer of the remaining tomatoes. Pour the remaining cream mixture evenly over the top.
7. Cover the dish and bake at 350 F for 1 hour. Remove the cover and bake for about 25 minutes more. Check to make sure the potatoes are nice and tender before proceeding to the next step.
8. Combine the breadcrumbs and the remaining 1 tablespoon olive oil in a small bowl. Stir together until the crumbs are well moistened with the oil. Spread the breadcrumb mixture over the top of the dish. Bake an additional 10 to 15 minutes at 350 F or until the breadcrumb layer is brown and crunchy. Remove from the oven and let cool on a wire rack 10 minutes before serving.