1. Weigh the flour accurately. In a stand mixer fitted with the paddle attachment, beat the butter until smooth. Add 1/2 cup flour. Mix until smooth. Scrape this dough into a flat square about 1 inch thick. The square should measure about 5 inches by 5 inches. Wrap well in plastic, and chill for at least 30 minutes.

2. In a large bowl, combine remaining flour with the salt. Gradually add the cream and mix until a rough dough is formed; it should not be sticky. Do not overmix. Roll the dough into a rectangle, about 12 inches by 7 inches, wrap in plastic, and chill, at least 30 minutes.

3. Remove the flour dough from the refrigerator and place on a lightly floured work surface. Place the butter square at the bottom edge of the rectangle, and fold the flour dough over to completely encase the butter, sealing the edges by pinching them together and forming tight hospital corners at the edges. Wrap well in plastic and chill for at least 30 minutes.

4. Remove the dough from the refrigerator. On a lightly floured board, gently pound the dough all over in regular intervals with a rolling pin. Working in only one direction (lengthwise), gently roll the dough into a 20-by-9-inch rectangle, squaring corners with a bench scraper and your hands as you go. Using a dry pastry brush, sweep off excess flour. With a short side facing you, fold the rectangle in thirds like a business letter, aligning the edges carefully and keeping each edge square. Turn the dough a quarter-turn clockwise, so the flap opening faces right, like a book. This completes the first turn. Pound across the dough, again in regular intervals, and roll out again to a 20-by-9-inch rectangle, rolling in the same lengthwise direction. Fold dough again into thirds. This completes the second turn. Wrap dough in plastic and refrigerate until well chilled, about 1 hour.

5. Repeat the rolling, turning, and chilling process for a total of six turns; always start each turn with the opening of the dough to the right, and always make your tri-fold in the same manner, that is, by starting from either the top of the dough or the bottom each time. By the sixth and final turn, the dough should be very smooth, with no lumps of butter visible. Use as little flour as possible for the rolling, and brush off any excess before folding the dough. If the dough becomes too elastic or too warm to work with, return it to the refrigerator until firm.

6. Wrap the finished dough in plastic and refrigerate until ready to use, at least 2 hours after your final turn, or freeze for future use.