01 - Preheat oven to 375°F. Grease an 8×8-inch baking dish with butter or nonstick spray.
02 - In a large, clean mixing bowl, beat the egg whites with an electric mixer on medium-high speed until stiff, glossy peaks hold their shape. Set aside.
03 - In a separate bowl, whisk together the egg yolks, cottage cheese, milk or cream, salt, pepper, and sweet paprika until smooth and well blended.
04 - Stir the shredded cheddar, grated Gruyère or mozzarella, sliced green onions, and any optional vegetables or herbs into the yolk mixture until evenly distributed.
05 - Gently fold the whipped egg whites into the cottage cheese mixture in two additions, using a spatula with light sweeping motions to preserve maximum volume.
06 - Pour the airy batter into the prepared baking dish and smooth the top with a spatula.
07 - Bake for 25 minutes, or until the top is deeply golden and the center is just set with a slight wobble.
08 - Allow the bake to rest for 5 minutes before slicing into portions. Serve warm alongside a fresh salad, roasted tomatoes, or crusty toast.