Make the dough: Whisk the salt and all-purpose flour together in a large bowl. Toss the butter in the flour mixture, squeezing and rubbing the butter into the flour. Dissolve the discard in the water. Create a well in the center of the flour and pour the dissolved discard into the center. Stir the mixture together until all the flour looks hydrated and no dry bits remain.

Chill the dough: Turn the dough out on to a large piece of plastic wrap, wrap it and flatten it out into a rectangle with sharp edges (this will make it easier to laminate).

Laminate the dough: Unwrap the dough and turn it out onto a heavily floured surface.

Complete Book Fold: Using a rolling pin, flatten the dough out into a large rectangle (about 18 by 8 inches, it doesn’t have to be exact). Fold the short sides towards so they meet in the center. Fold the dough in half and let it chill for 30 minutes.

Complete Letter Folds: Roll the dough out into a long rectangle (about 24 by 8 inches long). Fold the sides towards the center, overlapping like you’re folding a letter. Complete 2 to 3 letter folds in 30 minute intervals. Wrap the dough and chill it in between folds. The dough should look cohesive and the butter will look more evenly distributed after the last fold.

Store: Roll the dough out into a large rectangle (about 12 by 8 inches). Cut two rectangular strips of parchment paper. Fold the dough in thirds, tuck a piece of parchment between folds. Refrigerate the dough for at least 2 hours before using. Use according to recipe instructions.