准备

• 将烤箱加热到350°F。黄油介质（1-1/2-夸脱）浅烤盘。
• 用轻盐水将大约一半的大锅填充，然后用高火煮沸。将菠菜加入少量，在枯萎时添加更多。当所有菠菜都放在锅中时，擦一分钟。在漏勺中排干，将冷水在菠菜上冷却以冷却。挤压冷却的菠菜以除去尽可能多的液体，然后将其切碎。
• Heat the milk or broth in a small saucepan or in the microwave until hot. Set a medium saucepan over medium heat and melt the butter. Add the onion and cook until translucent and softened but not colored, about 5 minutes. Stir in the flour, salt, pepper, and cayenne and cook, stirring constantly, for 2 minutes. Slowly stir in the milk or broth, raise the heat to medium, and cook, stirring frequently, until the sauce bubbles and thickens, about 5 minutes.
• 当酱准备好了,添加Parmigia 1杯no and stir until the cheese is melted and thoroughly combined. Take the pan off the heat and stir in the chopped spinach, mixing well. Taste and season with more salt if necessary. Scrape into the buttered baking dish, sprinkle the remaining 1/4 cup Parmigiano on top, and bake until the gratin is bubbly and the top is nicely browned, 35 to 40 minutes. Let it cool for a few minutes before serving.