Détrempe (Base Dough):
Form a well in the sifted flour on your work surface. Pour in the water mixed with the salt, then incorporate 150 g of softened butter (not melted). Knead into a smooth dough and let it rest for at least 3 hours.
Tours (Folding):
Roll out the détrempe on a lightly floured surface. Place the remaining 750 g of cold butter in the center and fold the dough over it like a wallet. Roll out lengthwise into a rectangle and fold into a wallet again. Repeat the roll and fold. Wrap in a tea towel and refrigerate for 1 hour. Repeat the process once more, then refrigerate another hour.
Divide the dough into four equal parts. Take one quarter, roll out lengthwise, and trim the edges with a large sharp knife for crisp layers. Cut into 10 rectangles (12 x 5 cm). Stack them, alternating orientation (upside down). Place parchment paper between each rectangle. Refrigerate. Repeat with the remaining quarters.
Bake to order on a lightly floured baking sheet—no need to flip.
