Zucchini Cheese Bake

Vegetables

• 2 tablespoons vegetable oil — divided
• 2 cloves garlic cloves — minced, divided
• 1 medium white onion — thinly sliced
• 4 medium zucchini — about 2 pounds, halved, sliced ¼ inch thick
• ½ teaspoon salt

Cream Mixture

• 2 large eggs — separated
• 1 cup sour cream
• 2 tablespoons all-purpose flour
• 2 teaspoons Worcestershire sauce
• ½ teaspoon dry mustard
• ¼ teaspoon ground red pepper — cayenne

Topping

• ¾ cup sharp cheddar cheese — shredded

1. Prepare the Oven and Dish: Position a rack in the center of the oven. Preheat oven to 350°F and lightly grease a 9-inch round or 8-inch square baking dish.
2. Cook the Onion: In a 12-inch skillet heat 1 tablespoon oil over medium-high heat. Add the sliced onion and cook 4 to 5 minutes, stirring occasionally, until softened and lightly browned. Add half the garlic and cook about 30 seconds, just until fragrant. Transfer the onion and garlic to a large bowl.1 tbsp vegetable oil, 1 garlic clove, 1 onion
3. Cook the Zucchini: Return the skillet to medium-high heat and add the remaining oil. Add the zucchini and cook 6 to 8 minutes, stirring often, until barely tender, lightly browned in spots, and the skillet is nearly dry. Add the remaining garlic during the final 30 seconds. Toss with salt and transfer to the bowl with the onion. If liquid pools in the bowl, drain the vegetables before assembling. Let the vegetables stand while preparing the cream mixture.1 tbsp vegetable oil, 1 garlic clove, 4 zucchini, ½ tsp salt
4. Prepare the Cream Mixture: In a clean medium mixing bowl beat the egg whites with a hand mixer on medium-high speed for 2 to 3 minutes, until they hold glossy stiff peaks but do not look dry. In another medium bowl whisk together the egg yolks, sour cream, flour, Worcestershire sauce, dry mustard, and ground red pepper until smooth. Fold about one-third of the egg whites into the sour cream mixture to lighten it, then gently fold in the remaining whites with a rubber spatula.2 egg whites, 2 egg yolks, 1 cup sour cream, 2 tbsp flour, 2 tsp Worcestershire sauce, ½ tsp dry mustard, ¼ tsp ground red pepper
5. Assemble the Casserole: Spread half the zucchini and onion mixture evenly in the prepared baking dish. Spoon the cream mixture over the vegetables and spread it gently to the edges. Top with the remaining zucchini mixture and sprinkle evenly with cheddar cheese.zucchini mixture, cream mixture, ¾ cup cheddar
6. Bake: Bake uncovered on the center rack for 25 to 30 minutes, until the filling is set with no wet movement in the center, the cheese is melted, and the top and edges are lightly browned. An instant-read thermometer inserted in the center should register 160°F.
7. Rest and Serve: Let the casserole rest for 10 minutes before serving warm.