01 - Combine flour, sugar, salt, and yeast in a large bowl, keeping yeast separate from salt. Pour in lukewarm milk, melted butter, and crack in the egg. Mix thoroughly until a sticky, cohesive dough forms.
02 - Knead the dough on a lightly floured surface for 7 to 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 and refrigerate for 30 minutes to firm the texture for lamination.
04 - Roll the chilled dough on a floured surface 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 of dough over the center, then fold the remaining buttered third on top. Rotate the dough 90 degrees so the open edges face you.
06 - Roll the dough again into a 12 x 16-inch rectangle. Perform another letter fold by folding into thirds. Wrap and refrigerate for 30 minutes.
07 - Repeat the rolling and folding process two more times, chilling 30 minutes between each turn, for a total of three complete lamination turns.
08 - After the final chill, roll dough to approximately 8 x 16 inches. Starting from a short edge, roll tightly into a cylinder to form the loaf shape.
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 1 tablespoon milk for the egg wash. Brush the entire surface of the risen loaf generously.
11 - Bake for 35 to 40 minutes until deeply golden brown and the loaf sounds hollow when tapped. Tent with aluminum foil if the top browns too quickly.
12 - Let the bread cool in the pan for 10 minutes, then transfer to a wire rack. Cool completely before slicing for clean, even cuts.