© Roy Schuurhuis. Choux Pastry is a dough designed to make hollow puffy pastries from. In Choux Pastry, steam is the leavener. The dough has a high moisture content which in the oven turns to steam and causes light pockets inside the pastry to form. The resultant pastries needs to be airy, crispy and light. The dough is first cooked on a stove, in order to make a paste that a lot of the initial water has evaporated from.