Ingredients
1 large egg plus 2 large egg whites
2 tablespoons grated aged cheese, such as Gruyere
2 teaspoons whole milk
Coarse salt and ground pepper
1 teaspoon extra-virgin olive oil
1/2 small shallot, minced
1 1/2 cups baby spinach
Nonstick cooking spray
2 cups salad greens
1/4 teaspoon cider, sherry, or red-wine vinegar
Preparation
Place a 1-cup ovenproof baking dish on a rimmed baking sheet and place in oven; preheat oven to 450 degrees. While oven is heating, whisk together egg and egg whites, 1 tablespoon cheese, milk, 1/4 teaspoon salt, and pinch of pepper. In a small skillet, heat teaspoon oil over medium; add shallot and cook until softened, about 2 minutes. Add spinach; cook until wilted, about 2 minutes. Season with salt and pepper. Stir spinach into egg mixture.
Remove heated dish from oven and coat with cooking spray. Immediately pour in egg mixture and top with 1 tablespoon cheese. Bake until frittata is puffed up and golden brown, about 15 minutes. Toss greens with vinegar and 3/4 teaspoon oil; season with salt and pepper. Serve frittata with salad.
