01 - Combine flour, sugar, salt, and yeast in a large bowl, keeping yeast separate from salt. Pour in lukewarm milk, melted butter, and egg. Mix thoroughly until a sticky, cohesive dough forms.
02 - Knead dough for 7 to 10 minutes until smooth and elastic. Transfer to a greased bowl, cover, and let rise for 1 hour or until doubled in volume.
03 - Punch down risen dough and shape into a rectangle. Wrap 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, leaving a 1-inch border.
05 - Fold the unbuttered third over the center, then fold the remaining third on top. Rotate the dough 90 degrees so the open sides face you.
06 - Roll dough again to 12 x 16 inches. Perform a letter fold by folding into thirds. Wrap and refrigerate for 30 minutes.
07 - Repeat rolling, folding, and chilling two more times for a total of three turns. Chill for 30 minutes after the final fold.
08 - Roll dough to approximately 8 x 16 inches. Roll tightly from the short edge into a cylinder, sealing the seam.
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 with 1 tablespoon milk until blended. Brush the entire surface of the loaf with egg wash.
11 - Bake for 35 to 40 minutes until deep 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. Cool completely before slicing for clean cuts.