Creamy Swiss Chard Gratin with Crispy Gnocchi

将烤箱预热至375°F，距火架10英寸。将一大锅盐水煮沸。去除瑞士甜菜的茎；修剪和丢弃的茎末端，剩余的茎切成薄片。切片片叶成1英寸厚的条。将叶子和茎加到沸水中；煮，经常搅拌，直到叶子枯萎，茎是酥脆的，1至2分钟。在漏勺中排干。让冷却15分钟。轻轻挤在水槽上以去除多余的液体。 Set aside.

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.

将剩余的2汤匙黄油和剩余的2汤匙油添加到锅中；用培养基煮至黄油融化。加入洋葱；用1/4茶匙盐和1/4茶匙黑胡椒粉调味。煮，偶尔搅拌，直到洋葱变软和半透明，约8分钟。

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.

在预热的烤箱中烘烤，直到在边缘冒泡20到25分钟。将烤箱温度提高到烤面包。（请勿从烤箱中取出烤盘。）烤直到在斑点变成褐色，大约4分钟。从烤箱中取出；让冷却5分钟。