3 tablespoons unsalted butter
4 cups red onion, chopped
2 tablespoons sugar
1 teaspoon fresh thyme leaves
3/4 teaspoon salt
1/2 teaspoon of ground black pepper
2 bunches kale, ] ribs removed, torn into 1 1/2-inch pieces
8 ounces Gruyère cheese, shredded
1/2 cup Parmesan cheese, grated
2 1/2 cups heavy cream
- Melt 1 tablespoon of the butter in a frying pan 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 frying pan 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 Gruyère 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 Circulon baking pan. Pour the cream over the kale then sprinkle with the remaining Gruyère 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.