Preheat oven to 350 degrees F (175 degrees C).

Place a steamer insert into a saucepan and fill with water just below the bottom of the steamer. Bring water to a boil. Add cauliflower, cover and steam until tender, 5 to 7 minutes. Cool to room temperature.

Blend cauliflower, mushrooms, and green onions in a blender until chopped but still chunky.

Separate egg yolks and egg whites into 2 bowls. Beat egg whites in a bowl using an electric mixer until medium peaks form.

Combine half-and-half, butter, and flour in a saucepan over low heat; cook and stir until the white sauce thickens, about 5 minutes. Cool slightly.

Stir the white sauce, Parmesan cheese, cauliflower mixture, egg yolks, turmeric, salt, pepper, and curry powder in a bowl. Gently fold in the egg whites using a spatula. Pour mixture into a glass baking dish and sprinkle paprika.