Makes 2 1/2 pounds of dough

Mixing the Dough: Put all-purpose flour, cake flour, and salt in the work bowl of a food processor fitted with the metal blade. Pulse just to mix. Add water all at once, pulsing until dough forms a ball on the blade. Remove dough from machine, form into a ball, and slash the top in a tic-tac-toe pattern, with a small sharp knife. Wrap dough in a damp towel and refrigerate 5 minutes.

Incorporating the Butter: Place butter between 2 sheets of plastic wrap and beat with a rolling pin until it flattens into a 1 inch thick square. Unwrap the chilled dough and place it on a work surface dusted with all-purpose flour. Roll into a 10-inch square. Starting from the center of the square, roll out over each corner to create a thick center pad with "ears" or flaps. Place the cold butter in the middle of the dough and fold ears over butter, stretching as needed so they overlap slightly and encase butter completely. It should be about 8 inches square.

Making the Turns: Gently but firmly press the rolling pin against the top and bottom edges of the square. Then, keeping the work surface and dough well floured, roll the dough into a rectangle that is three times as long as the square you started with, about 24 inches. (Don't worry about the width of the rectangle; if you get the 24 inches, everything else will work itself out.) With this first roll, it is particularly important that the butter be rolled evenly along the length and width of the rectangle; check when you start rolling that the butter is moving along well, and roll a bit harder or more evenly, if necessary, to get a smooth, even dough-butter sandwich. With a pastry brush, brush off the excess flour from the top of the dough, and fold the rectangle up from the bottom and down from the top in thirds, like a business letter, brushing off the excess flour. You have completed one turn.

Rotate the dough so that the closed fold is to your left, like the spine of a book. Repeat the rolling and folding process, rolling the dough to a length of 24 inches and then folding in thirds. This is the second turn.

Chilling the Dough: If the dough is still cool and no butter is oozing out, you can give the dough another two turns now. If the condition of the dough is iffy, wrap it in plastic wrap and refrigerate it for at least 30 minutes. Each time you refrigerate the dough, mark the number of turns you've completed. It is best to refrigerate the dough for 30 to 60 minutes between each set of two turns.

The total number of turns needed is six.