In a stand mixer, blend the all-purpose flour, granulated sugar, salt, and instant yeast, ensuring to keep the yeast separate from the salt initially. Then, pour in the room temperature water and whole milk; mix until the dough is smooth.

Form the dough into a ball, cover it with a clean kitchen towel, and let it rest in a warm place for at least 30 minutes.

Blend the chilled unsalted butter with some additional flour until creamy. Shape the mixture into a square and chill it until firm.

Roll the rested dough into a large square. Place the chilled butter square in the center, fold the corners over the butter, sealing tightly, and chill for 60 minutes.

Roll the dough into a rectangle, then fold into thirds. Repeat this rolling and folding process two more times, resting the dough in the refrigerator for 30 minutes between each turn.

Divide the dough, roll it into a rectangle, and cut into triangles. Roll each triangle from the wide end towards the point to form the croissants.

Place the shaped croissants on a baking sheet lined with parchment paper, cover lightly, and let rise until doubled in size, about 60-90 minutes.

Preheat your oven to 375°F (190°C). Brush croissants with the beaten egg wash and bake for about 20 minutes or until golden brown.