The owners of this place are Polish so maybe not into pickled onions or eggs. They do a sideline menu only written in Polish so I don’t know what’s on it but it always smells good. My local place in Norn Iron doesn’t sell pickled stuff either – maybe it’s a regional thing?
I do remember one of my first jobs in my late teens working in an old man’s bar, when a guy asked me for an egg I didn’t know what the fuck he meant, thought he wanted me to go fry him one. Had to ask another staff member and they explained it was a cooked egg soaked in vinegar. Thought it sounded a bit rank at the time and I’ve never tried one since.