I’ve consulted with two restaurants where the training at the Culinary Academy and the Cordon Bleu gave the chefs the wrong approach.
Chefs are often trained to look at the returning dishes to determine what menu items are unpopular and are left on the plate. The theory is that this is a clue that will suggest replacements for menu revisions.
In one case, the client was a high end elegant vegetarian restaurant and the other case was a new, highly admired Italian top quality white tablecloth North Beach spot.
In both cases when they first opened to rave reviews, I was asked for advice on continuing their success. They had listened to me before opening when I told them to open full and stay full the first month, no matter how many meals they had to give away.
My advice on continuing success was ‘don’t look at the returning dishes’. Don't use that information to shape your menu.
The reason is that at a table of four, one is the vegetarian that the other three acceded to when coming to a vegetarian restaurant. In the case of the Italian gourmet restaurant, one diner was the gourmet with refined taste and the other three were deferring to his or her taste.
By adjusting the menu, based on returned dinner plates, you risked being guided by the palate of the three people who did not choose the restaurant in the first place. Use the chef’s feel for food and the menu. The chef knows what his/her diners appreciate.