This section is from the book "The Steward's Handbook And Guide To Party Catering", by Jessup Whitehead. Also available from Amazon: Larousse Gastronomique.
A cursory examination of the hotel bills of fare from all parts of the country will show that the custom of serving potatoes in some fancy form with fish has become very general, so much so that a bill does not seem to be complete nor as stylish as it might be if that feature happens to have been omitted. It is a recent custom which originated in the famous restaurants of Paris, notably at Brebant's, for whom one of the forms of potatoes is named, that we designate a la Brabant. It comes quite as natural to eat vegetables with fish as with meat, yet foreign custom, and particularly English custom, has confined us heretofore to bread - generally brown bread - with that course. The ornamental addition of potatoes to the sauce is the more satisfactory, because the individual style of service of the present day shuts out most of the ornamental styles of dishes that used to be served whole. Potato croquettes and croquette balls, leaf, heart and star shapes of duchesse potatoes carefully egged over and baked, and, indeed, all the variations that are in use are great helps to the appearance of a plate of fish.
New waiters generally have to be instructed on this point, as they are most apt to take a meat dish for fish. But if they serve it so, the person at table will slip it from the dish to his plate, and the dinner plate will then have to be changed for the meat course. Apart from that consideration, the fish looks better on a dessert plate, and it cannot be transferred to another without "mussing" it up with its sauce. The diner eats it from its own small plate, garnished as the cook sends it in.