Lunch: Winter Greens Gratin

Recipe by The Bon Appétit Test Kitchen Blanching the mustard greens and kale ahead of time both softens them up and helps keep their color.

This recipe includes superfoods such as:

Kale

Health benefits of Winter Greens Gratin

Kale is an excellent source of calcium, which has an important role in egg maturation and follicle development in the ovaries.

Ingredients

1 tablespoon unsalted butter plus more for dish
2 pounds kale, center ribs and stems removed, torn into large pieces, or two 10-ounce bags trimmed, chopped kale (about 24 cups)
Kosher salt
2 1/2 pounds mustard greens, center ribs and stems removed, torn into large pieces
1/4 cup extra-virgin olive oil
3 cups coarse fresh breadcrumbs
1/2 cup finely grated Parmesan
2 teaspoons fresh thyme leaves, divided, plus 7 sprigs thyme
2 shallots, sliced into 1/4"-thick rounds (about 1 cup)
1 cup heavy cream
1 cup whole milk
7 garlic cloves, smashed
1/8 teaspoon freshly ground nutmeg
Freshly ground black pepper
1 cup coarsely grated Gruyère

Instructions

Lightly butter a 3-quart baking dish. Working in batches, blanch kale in a pot of boiling lightly salted water until just softened, about 3 minutes. Using a slotted spoon, transfer kale to a large bowl of ice water; let cool, then drain. Squeeze out as much excess water as possible by hand and transfer kale to a work surface.
Repeat with mustard greens, blanching for 2 minutes per batch. Coarsely chop all greens and combine in a large bowl (you should have 6 cups tightly packed greens). Separate clumps and loosen chopped leaves by hand.
Heat oil in a 12" skillet over medium heat. Add breadcrumbs and cook, stirring frequently, until golden and crispy, 8-10 minutes. Transfer to a large bowl; stir in Parmesan and 1 teaspoon thyme leaves. DO AHEAD: Greens and breadcrumbs can be made 2 days ahead. Cover greens and chill. Store breadcrumbs airtight at room temperature.
Melt 1 tablespoon butter in a medium saucepan over medium-high heat. Add shallots; cook, stirring often, until slightly softened and light golden, about 5 minutes. Transfer shallots to bowl with greens. Add cream, milk, garlic, and thyme sprigs to same saucepan; bring to a simmer. Cook until mixture is thickened and reduced to 1 1/2 cups, 10-12 minutes. Discard thyme sprigs and garlic; stir in nutmeg. Season mixture with salt and pepper.
Pour cream mixture over greens in bowl and toss to evenly coat in sauce; season to taste with salt and pepper. Transfer greens mixture to prepared baking dish; sprinkle Gruyère over. Top with breadcrumbs. Cover dish with foil. DO AHEAD: Gratin can be assembled 1 day ahead.
Preheat oven to 400 °F. Bake until filling is hot, about 25 minutes. Uncover and bake until cheese is melted, edges are bubbling, and breadcrumbs are golden brown, 10-20 minutes longer. Garnish with remaining 1 teaspoon thyme leaves.