In a medium saucepan, add the water and butter over medium heat. Once melted, whisk in the flour, reduce heat to low, and cook, continuing to stir, until the dough lifts from the sides and bottom of the pan. Remove from heat and allow to cool.
Beat the eggs into the dough, one at a time, until well-combined, followed by the baking powder.
Divide the dough into two equal pieces. Place each piece on the prepared baking sheet and press into equal rectangles about 1/4 inch thick.
Bake in the preheated oven until puffed and golden, 15 to 20 minutes. Do not open the oven door until it is nearly done. Remove and allow to cool to room temperature.