What do you crave? Why do you crave it? I ask these questions because of a craving in my own life...for a milkshake. Now, this is not just ANY milkshake, but the mother of all milkshakes. This milkshake has power. Have you ever felt like that about something? That it had the power to take over your thoughts, your dreams, your every craving? I have. The culprit: the limited-time-only "Birthday Cake Shake" at Zaxby's restaurant.