This one’s really vague. Some sort of animal (a dog? pig? cat? Susan?) roams the countryside at night. It encounters a creature with a magic bag full of whatever sandwich you want. The illustrations were all black and white and it was a small book.
Stump the Bookseller
New format, same book stumper solving.
This is a long shot, but I think you are remembering Maurice Sendak’s beautiful Higglety Pigglety Pop; Or, There Must be More to Life (1967). A white scotty dog, Jenny, sets out from her life of comfort to discover what else life has to offer. On her way she meets a pig wearing a sandwich board advertising an acting job. She eats all of his sandwiches (and many other things) before her adventures are over. It is a small book with detailed b+w drawings, including Jenny wandering the countryside at night. You can find a reproduction of many illustrations (including the pig in a sandwich board) here: http://vintagechildrenbooks.blogspot.com/2012/06/higglety-pigglety-pop-or-there-must-be.html
Amazing, that’s it, thank you so much! Oh my goodness what a relief.