01 - Preheat oven to 375°F (190°C). Grease a medium baking dish (about 8x8 inches or 2 liters) with butter or nonstick spray.
02 - In a large clean bowl, beat the egg whites with an electric mixer on medium-high speed until stiff peaks form. Set aside.
03 - In a separate bowl, whisk together the egg yolks, cottage cheese, milk or cream, salt, black pepper, and sweet paprika until smooth and well combined.
04 - Stir the shredded cheddar, grated Gruyère or mozzarella, sliced green onions, and any optional vegetables or herbs into the yolk mixture.
05 - Gently fold the whipped egg whites into the cottage cheese mixture in two stages, maintaining as much air as possible to preserve the cloud-like texture.
06 - Pour the fluffy mixture into the prepared baking dish and level the top with a spatula.
07 - Bake for 25 minutes, or until the top is puffed, golden brown, and the center is fully set.
08 - Allow the bake to cool for 5 minutes before slicing into portions and serving.