Fo me, it’s not a special menu. It’s dinner for the following night, the regular menu. I select what I want and the headwaiter has it prepared within my dietary restrictions (no dairy). When we sit down the following night, I tell my server I have pre ordered and the name of my headwaiter. After a night or two, they remember.
I ask at the buffet, and someone from the kitchen wearing a tall hat tours me through the line and tells me what I can or cannot eat.