Adapted from Bon Appetit Magazine
- 1 tablespoon butter, unsalted, plus more for dish
- 2 pounds kale, center ribs and stems removed, torn into large pieces
- 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” 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 Gruyere
Lightly butter a 3 quart ceramic baking dish. Working in batches, blanch kale in pot of boiling lightly salted water until just softened, about 3 minutes. Using a slotted spoon, transfer kale to a colander and run cold water over. Once cooled, 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. 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 bowl; stir in Parmesan and 1 tsp thyme leaves, set aside.
Wipe out skillet and melt one tablespoon butter. 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 skillet; bring to simmer. Cook until mixture is thickened and reduced to 1 1/2 cups,
8 minutes. Discard thyme sprigs and garlic; stir in nutmeg. Season with 1 teaspoon kosher salt and 1/2 teaspoon pepper.
Pour cream mixture over greens in bowl and toss to evenly coat in sauce; season to taste. Transfer greens mixture to prepared baking dish; sprinkle Gruyere over. Top with breadcrumbs and cover dish with foil.
Bake until filling is hot, about 20 minutes. Remove the foil an continue to cook for 2-3 minutes or until bread crumbs are golden brown. Garnish with remaining thyme leaves.