01 - Preheat the oven to 375°F. Lightly grease an 8x8-inch baking dish with butter or nonstick spray.
02 - In a large, clean mixing bowl, beat the egg whites using an electric mixer on medium-high speed until stiff, glossy 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 fresh 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 and careful folding motions to preserve as much volume and air as possible.
06 - Pour the light, fluffy batter into the prepared baking dish and use a spatula to spread it evenly, smoothing the top.
07 - Bake on the center rack for 25 minutes, or until the top is deeply golden, the edges are puffed, and the center is fully set.
08 - Remove from the oven and allow the bake to rest for 5 minutes before slicing into portions and serving warm.