Blend the two flours together in a 4-quart mixing bowl. Remove 1/2 cup of the flour and reserve.
Stir the oil into the flour and mix thoroughly with a rubber spatula. Then stir in the salt and the water, cutting and pressing ingredients firmly into a mass with spatula and then with the cupped fingers of one hand. Place on pastry marble or board. Sprinkle any unmassed bits of flour left in the bowl with drops of water; press together and add to dough.
On the board, press dough firmly and rapidly into a cushion shape. Sprinkle it lightly with flour, wrap in waxed paper and refrigerate 40 minutes.
Beat the butter with a rolling pin to soften it. Smear it out with a scraper or the heel of your hand. Work in the reserved flour until the mixture is perfectly smooth and of spreading consistency, but still cold.
Lightly flour the dough and your hands. Push the dough with your hands into a rectangle, 16 to 18 inches long and about 8 inches wide. Using a stiff spatula, spread the softened butter over the upper two-thirds of the dough, leaving an 1/8-inch border unbuttered. Fold the unbuttered third up to the middle; fold the top third down to cover it.
Rotate the dough a quarter turn and roll it out to 18 inches long and 8 inches wide. Fold the top and bottom edges of the rectangle so they meet in the center of the dough. Fold them together again. You now will have eight layers of butter sandwiched in between nine layers of dough.
Wrap the dough in waxed paper, then a plastic bag, and refrigerate for 40 to 60 minutes.
Unwrap the chilled dough and flour it sparingly top to bottom. Roll dough rapidly out into a rectangle 18 long and 8 inches wide. Fold the rectangle of dough into thirds again; roll it into a rectangle and fold again into three. Make 4 depression marks into dough with the ball ends of your fingers. Wrap the dough again and chill for 2 hours to firm the butter and to relax the gluten. It is now ready for forming and baking in any way your recipe directs.