01 - Combine flour, sugar, salt, and yeast in a large bowl, keeping yeast separate from salt. Pour in lukewarm milk, melted butter, and cracked egg. Mix thoroughly until a sticky, cohesive dough forms.
02 - Knead the dough on a floured surface for 7–10 minutes until smooth and elastic. Transfer to a greased bowl, cover, and let rise for 1 hour until doubled in volume.
03 - Punch down the risen dough and shape into a rectangle. Cover tightly and refrigerate for 30 minutes to firm the gluten.
04 - On a lightly floured surface, roll the chilled dough into a 12 x 16-inch rectangle. Arrange cold butter slices over two-thirds of the dough surface, leaving a 1-inch border.
05 - Fold the unbuttered third over the center, then fold the remaining third over to create a neat rectangular packet. Rotate the dough 90 degrees so the open ends face you.
06 - Roll the dough again into a 12 x 16-inch rectangle. Perform a letter fold by folding into thirds. Wrap in plastic and refrigerate for 30 minutes.
07 - Repeat the rolling and folding process two more times, chilling for 30 minutes between each turn. This creates a total of three complete turns for maximum flakiness.
08 - After the final chill, roll the dough to approximately 8 x 16 inches. Roll tightly from the short end into a cylinder, sealing the seam securely.
09 - Place the loaf seam-side down in a greased 9 x 5-inch loaf pan. Cover loosely and let rise until doubled, about 1 hour.
10 - Preheat oven to 375°F. Whisk together egg and milk for the egg wash. Brush the entire surface of the risen loaf evenly with the mixture.
11 - Bake for 35–40 minutes until deep golden brown and the loaf sounds hollow when tapped. Tent loosely with foil if the top browns too quickly.
12 - Let the loaf cool in the pan for 10 minutes, then transfer to a wire rack. Cool fully before slicing to preserve the layered structure.