Ingredients
- 1 1/2 pounds Swiss chard (about 3 bunches)
- 1/4 cup unsalted butter, divided
- 1/4 cup extra-virgin olive oil, divided
- 2 (12-ounces) packages refrigerated potato gnocchi (such as Giovanni Rana Skillet Gnocchi), divided
- 1 1/2 teaspoons kosher salt, divided
- 3/4 teaspoon black pepper, divided
- 1 large red onion (about 12 ounces), thinly sliced (about 2 1/2 cups)
- 1/3 cup all-purpose flour (about 1 1/2 ounces)
- 3 1/4 cups whole milk
- 2 ounces Gruyère cheese, shredded (about 1/2 cup)
- 2 ounces Parmigiano-Reggiano cheese, grated (about 1/2 cup)
- 1 1/2 tablespoons Dijon mustard
- 1 teaspoon grated garlic
- 1/4 teaspoon cayenne pepper
- 1/4 teaspoon ground nutmeg
Description
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Preheat oven to 375°F with rack 10 inches from heat. Bring a large pot of salted water to a boil over high. Remove stems from Swiss chard; trim and discard stem ends, and thinly slice remaining stems. Slice chard leaves into 1-inch-thick strips. Add leaves and stems to boiling water; cook, stirring often, until leaves are wilted and stems are crisp-tender, 1 to 2 minutes. Drain well in a colander. Let cool 15 minutes. Gently squeeze over sink to remove any excess liquid. Set aside.
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Wipe pot clean. Add 1 tablespoon butter and 1 tablespoon oil; cook over medium-high until butter melts. Add 1 package of gnocchi; cook, turning gnocchi occasionally, until golden brown and crisp, 5 to 7 minutes. Transfer to a baking sheet. Repeat process with 1 tablespoon butter, 1 tablespoon oil, and remaining gnocchi. Season all gnocchi with 1/2 teaspoon salt and 1/4 teaspoon black pepper. Set aside.
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Add remaining 2 tablespoons butter and remaining 2 tablespoons oil to pot; cook over medium until butter melts. Add onion; season with 1/4 teaspoon salt and 1/4 teaspoon black pepper. Cook, stirring occasionally, until onion is softened and translucent, about 8 minutes.
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Sprinkle onion mixture with flour; cook over medium, stirring constantly, 2 minutes. Gradually whisk in milk until smooth. Bring just to a simmer over medium-high, whisking occasionally. Reduce heat to low; gently simmer, whisking often, until mixture is thickened, about 5 minutes. Remove from heat. Stir in Gruyère, Parmigiano-Reggiano, mustard, garlic, cayenne, and nutmeg. Fold in gnocchi and chard. Season with remaining 3/4 teaspoon salt and remaining 1/4 teaspoon black pepper. Spread mixture evenly into an 11- x 7-inch broiler-safe baking dish; place baking dish on a baking sheet lined with parchment paper to catch drips.
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Bake in preheated oven until bubbling around edges, 20 to 25 minutes. Increase oven temperature to broil. (Do not remove baking dish from oven.) Broil until browned in spots, about 4 minutes. Remove from oven; let cool 5 minutes.