We believe caramelized onions may be the key to all culinary success—they make just about everything taste better! In this gratin, they are the perfect sweet, soft foil to hearty kale. The key to making achingly sweet, meltingly delicious caramelized onions is to take it nice and slow. Higher heat will cook the onions, but they won’t caramelize.
- 3 tablespoons unsalted butter
- 4 cups red onion
- 2 tablespoons sugar
- 1 teaspoon fresh thyme leaves
- 3/4 teaspoon salt
- 1/2 teaspoon ground black pepper
- 2 bunches kale, ribs removed, torn into 1 1/2-inch pieces
- 8 ounces Gruyere cheese, shredded
- 1/2 cup Parmesan cheese, grated
- 2 1/2 cups heavy cream
- Melt 1 tablespoon of the butter in a large Anolon skillet over medium heat. Add the onion, sugar, thyme, 1/4 teaspoon of the salt and 1/4 teaspoon of the pepper; cook, stirring occasionally, until golden, about 18-20 minutes. Transfer to a bowl.
- Preheat the oven to 425°F.
- Wipe out the skillet and melt 1 tablespoon of the remaining butter over medium heat. Add half of the kale and cook, tossing, until slightly wilted, about 1 1/2 minutes. Transfer kale to the bowl with the onions; repeat with the remaining butter and kale.
- Add half of the Gruyere cheese, 1/4 cup of the Parmesan cheese, remaining 1/2 teaspoon salt and 1/4 teaspoon pepper to the kale mixture and toss well. Transfer to a 9 by 13-inch baking dish. Pour the cream over the kale then sprinkle with the remaining Gruyere and Parmesan cheeses.
- Bake in the center of the oven until the cream has thickened and the cheese is golden brown, about 53-55 minutes. Let stand 10 minutes before serving.