In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, salt, and instant yeast until well combined.

Gradually add the warmed whole milk and softened unsalted butter, mixing until a shaggy dough forms.

Turn the dough onto a floured surface and knead for 5-7 minutes until smooth and elastic.

Place the dough ball into a greased bowl, cover with plastic wrap, and let it rise in a warm area for about 1 hour.

After the dough has risen, turn it out onto a floured surface and roll it into a rectangle 18x12 inches.

Place the cold, cubed unsalted butter in the center and fold the dough over to encase the butter.

Roll the dough out again into a rectangle about 18x12 inches and fold it into thirds, then refrigerate for 30 minutes.

Repeat the rolling and folding process two more times, each time refrigerating for 30 minutes.

After the final chilling, roll the dough into a large rectangle, shape it into your desired loaf shape, and place it in a greased loaf pan.

Cover the loaf pan with plastic wrap and let the dough rise for about 30-45 minutes.

Preheat your oven to 375°F (190°C) while the dough is rising.

In a small bowl, whisk together the egg and milk to create an egg wash, then brush it over the top of the loaf.

Bake the loaf in the preheated oven for 25-30 minutes, until golden brown and the internal temperature reaches 190°F (88°C).

Allow the loaf to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.