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Spiced Tomato Potato Gratin
(recipe, Katie Hickey)
Got the original recipe from Heidi Swanson. She called for heavy cream, which I got rid of and used a combination of milk and half and half. Turned out great.
- 1 tsp. whole cumin seeds
- 2 tsp. curry powder (I used mostly garam masala, I think, with some madras for heat)
- ½ tsp. red pepper flakes
- extra-virgin olive oil
- 6 cups thinly sliced yellow onions (about 2 pounds / 32 oz / 910 g)
- ½ Tbsp. unsalted butter
- 1¼ lb. / 20 ounces / 570 g Yukon Gold potatoes
- ½ cup / 120 ml combination of milk and half and half (I did about ½ milk, ½ H&H)
- 2 lb. / 32 oz / 910 g ripe tomatoes
- a small handful of basil leaves, slivered
- sea salt and freshly ground pepper
- Preheat the oven to 350F / 180C with a rack in the top third.
- Combine the spices in a small bowl and set aside.
- You can get a jump start on the onions while you slice the potatoes and tomatoes. Heat olive oil in your largest skillet or dutch oven over high heat. When hot, stir in the onions along with a few pinches of salt. Cook for a few minutes, stirring often, until the onions soften up - 4-5 minutes. Turn the heat down to medium and stir in the butter. Stirring regularly, cook another 10 - 15 minutes at this temperature, or until the onions just begin to caramelize a bit. Dial the heat back a shade more, and cook until the onions are deeply golden, this might take another 20 minutes. A minute before the onions are finished cooking stir in the spice mixture. Remove the pan from heat and set aside the onions.
- In the meantime, use a mandoline to slice the potatoes into ⅛-inch thick rounds. Place in a medium bowl along with the milk/half&half, 1 teaspoon of salt, and bit of pepper. Toss well, and set aside.
- Use a knife to cut the tomatoes into ¼-inch thick slices. Arrange across a large plate and sprinkle with another teaspoon of salt and some pepper.
- Smear half the caramelized onions across the bottom of a 10x10 inch (or equivalent) gratin or baking dish. Take half of the potatoes and half of the tomatoes and arrange on top of the onion layer (see photo). Drizzle with a couple tablespoons of milk from the potatoes and a drizzle of olive oil. Season the layer with a pinch of salt and half the basil.
- Scatter the remaining onions across the potatoes and tomatoes already in the pan. Then arrange another layer of tomatoes and potatoes on top. This will be the top of your gratin, so do your best to make it look nice. Pour the remaining milk, from the potatoes, and another drizzle of olive oil across the top. Season with another pinch of salt and the remaining basil. Gently press down on the vegetables so the milk comes up through the layers of vegetables evenly.
- Cover tightly with aluminum foil and bake for 2 hours, or until the potatoes are completely tender throughout. Increase the oven to 450F / 230C, carefully uncover the gratin, and cook another 30 minutes, or until the top takes on a nice golden color.