A new book takes a crack at defining it. "The Essential Mormon Cookbook", reviewed with some recipes here. http://deseretnews.com/dn/view/0,1249,595060828,00.html
I doubt that the sample recipes will stir much interest here, nor should they by and large.
If I had to list what I would call "mormon food", the green jello would make the list as would "funeral potatoes"--a dish made of potatoes, onions, cheese, sourcream and a whitesauce or canned cream of * soup.
I do want to read this cookbook just to see what other cultural dishes have made the grade to official "mormon food".