01 - In a large bowl, combine flour, sugar, salt, and yeast, placing yeast away from direct salt contact. Add lukewarm milk, melted butter, and egg. Mix until a sticky dough forms.
02 - Knead the dough for 7 to 10 minutes until smooth and elastic. Cover and let rise in a greased bowl for 1 hour or until doubled in size.
03 - Punch down dough and shape into a rectangle. Cover and refrigerate for 30 minutes.
04 - On a lightly floured surface, roll dough into a 12 x 16-inch rectangle. Layer cold butter slices over two-thirds of the dough.
05 - Fold the unbuttered third over the butter, then fold the remaining third over to form a neat rectangle. Rotate 90° so openings face you.
06 - Roll into a 12 x 16-inch rectangle again. Fold into thirds (letter fold), wrap, and chill for 30 minutes.
07 - Repeat rolling, folding, and chilling process two more times for a total of three turns.
08 - After the final chill, roll dough to approximately 8 x 16 inches. Roll up tightly from the short edge into a loaf shape.
09 - Place 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 egg and milk for egg wash. Brush loaf surface thoroughly.
11 - Bake for 35 to 40 minutes until golden brown and sound hollow when tapped. Tent with foil if browning too quickly.
12 - Cool in pan for 10 minutes, then transfer to wire rack to cool fully before slicing.