01 - In a large bowl, combine flour, sugar, salt, and yeast, positioning yeast away from direct salt contact. Pour in lukewarm milk, melted butter, and egg. Mix thoroughly until a sticky, cohesive dough forms.
02 - Knead the dough for 7 to 10 minutes until smooth and elastic. Transfer to a greased bowl, cover, and allow to rise for 1 hour or until doubled in volume.
03 - Punch down the risen dough and shape into a rectangle. Cover tightly and refrigerate for 30 minutes to firm.
04 - On a lightly floured surface, roll 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 butter section, then fold the remaining third on top to create a neat rectangle. Rotate the dough 90° so the open edges face you.
06 - Roll 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, folding, and chilling process two additional times for a total of three complete turns. Chill for 30 minutes between each turn.
08 - After the final chill, roll dough to approximately 8 x 16 inches. Roll tightly from the short edge into a loaf shape, pinching the seam to seal.
09 - Place the loaf seam-side down in a greased 9 x 5-inch loaf pan. Cover loosely with plastic 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.
11 - Bake for 35 to 40 minutes until deeply golden brown and the loaf sounds hollow when tapped. Tent loosely with foil if browning too quickly.
12 - Let cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing for clean, even cuts.