A couscoussier is a specialty pan made for cooking couscous. A couscoussier consists of two pans, one is set on top of the other, where the top pan has a perforated bottom for steaming.
It is similar to a steamer pan only the bottom is meant to cook actual food in such as a stew – not simply to just hold the water for steaming. The top captures the steam as the food is cooking below and gently cooks the couscous. The bottom pan can work independent from the top.