How to Pack Lunch (Businesswomen's Edition), 1889

Godey's Ladies' Book, December 1884

"Portable Lunches... To women breadwinners how to have some change from the fare they daily carry with them, and which, perhaps, has long since palled on their tired palates, is a very puzzling and important question…  It will seem almost a mockery, perhaps, to tell tired business women to do anything that will encroach on their precious time. Yet good, enjoyable food is health, and, if they are well nourished, they will be more vigorous, and perhaps feel more inclined to take a little trouble… 

Chocolate sandwich.
Cut thin slices of bread and butter as for other sandwiches, have a cake of sweetened chocolate in a warm spot over night, or long enough to become soft like cheese. Scrape it and spread thickly over the bread and butter, then make into sandwiches. This sandwich, when the appetite is jaded and craves variety, will be agreeable to chocolate lovers. A cake of chocolate between two crackers is another form of it." 

Mrs. John A. Logan, The Home Manual

Age-old secret of successful businesswomen: the chocolate sandwich.