Thomas Keller's ad hoc, which literally means for this purpose, was originally intended to be a temporary restaurant, open during the development of a very different concept. But, due to its loyal following, it was decided that it must be a permanent fixture in Yountville. ad hoc serves a prix fixe, 4-course chalkboard menu, changing daily. Food is served family style and reminiscent of the comfort food with which Chef Keller grew up.