Working quickly, lay the thawed puff pastry onto a large cutting board or other clean kitchen surface and, if necessary, gently roll it out according to package directions. Using a pizza wheel, cut it slightly larger (about 1-inch larger) than the baking dish, as necessary. (Note: If you have any pastry scraps, save them for other purpose.) Again, working quickly, lay the pastry sheet onto the chicken mixture. Using your fingers, press the pastry onto the rims of the baking dish.