Every fall, I make Martha Stewart's Pumpkin Chocolate Chip Squares. They're always a huge hit and I absolutely adore the pumpkin and chocolate combination (see my dad's recipe for Pumpkin Chocolate Chip Muffins here).
They're so good and easy to make. I use Earth Balance instead of butter, 1 T ground flaxseeds + 3 T water instead of the egg, and vegan chocolate chips.
During the holidays, I give them as gifts and leave a note letting the recipient know they're vegan!