When the dough has chilled. cut each half into 3 pieces. Roll each piece into a rough circle, that's maybe about 6" in diameter. As you are working with each piece, you might want to place the other pieces in the fridge, especially if it's too warm in your kitchen. Slowly pick up the rolled out dough and place it on a piece of plastic wrap. Repeat this with remaining pieces, placing each piece on top of each other with a plastic wrap in between. Place them back in the fridge while you make the filling.
Turn the dough over onto a floured surface and form it into a ball. Cut the ball into 2 pieces, and flatten each one into a disk. Wrap in plastic wrap and refrigerate for at least an hour.
To make the pastry you can use a food processor or just do it by hand. In a bowl the flour, cornmeal, salt, sugar and butter. Using two knives or a pastry cutter, cut in the butter until it resembles course sand. When ready, add the water and mix it all together until the dough sticks together.