Make dough. In a stand mixer, combine yeast, warm water, and sugar. Let sit 5 minutes until foamy. Add warm milk, salt, and bread flour; mix to combine. Slowly add all-purpose flour until the dough pulls from the sides of the bowl. Mix in butter and knead about 5 minutes until smooth and soft.
Risse. Coat a clean bowl with oil. Place dough inside, turn once to coat, and cover. Let rise in a warm place for about 2 hours, or until doubled in size.
Make butter layer. For the butter layer, beat together 2 tablespoons flour and 1 cup butter until smooth. Spread into a rectangle (about 8×13 inches) on parchment paper. Cover and chill while the dough rises.
Laminate. Roll risen dough into a large rectangle (about 18×26 inches). Place butter layer on half the dough and fold over to seal. Chill 30 minutes, then roll out and fold into thirds. Repeat this roll–fold–chill process 3 more times (4 total folds), chilling 30 minutes between each.
Roll out and shape. After the final chill, roll dough into a ½-inch thick rectangle. Cut into 12 long triangles, make a small slit at the wide end, and roll into crescent shapes. Place on parchment-lined baking sheets, cover, and rise 30 minutes.
Final rise. Place on parchment-lined baking sheets, cover, and rise 30 minutes.
Bake. Preheat oven to 375°F. Brush tops with egg wash. Bake 25 minutes or until deep golden brown. Cool slightly before serving.