Shortbread is a classic, eggless dough that pair nicely with almost anything you'd like to add. The cookies are nice and crisp, and work so well as a backdrop. Don't think they are plain, though! They are so easily dressed up you might not want to eat them without additions again.
Not only is shortbread easy to slice and bake, you can also pipe it or shape it into anything you can imagine. I also like to use it as a crust for traditional lemon bars.