Measure all ingredients.
Add flour and cubed butter to the bowl of a stand mixer fitted with the dough hook.
Mix flour and cubed butter on low speed until a coarse meal texture is achieved (like pie dough). Be CAREFUL not to over mix, there should still be small chunks of butter visible.
Dissolve salt in cold water. With mixer running on low speed, add water/salt mixture. Mix just until the dough is combined.
Mix water with flour & butter just until the dough is combined.
Dump dough onto a flat work surface. Knead once or twice to achieve a cohesive dough.
Using a rolling pin, perform a single fold by rolling dough into a large rectangle, about 1 cm / ½ inch thick.
Fold in thirds = left side to center and fold right side over center. It should have three folds (like a letter). Repeat twice more (for a total of three single folds).
Lastly, perform a double fold by rolling dough into a 1 cm / ½ inch thick rectangle. Fold left side to center fold. Fold right side to meet the end of the left side so there is an open seam in the center, like a book laying open flat.
Then fold in half along the open seam. It should now have 4-layers. Do not roll again.
Cut the 4 layer dough into four equal pieces, about 330 grams per piece.
Place the dough in the refrigerator while you prepare the apple filling.