Activate Yeast: Combine warm milk and sugar in a mixing bowl, stir until dissolved, sprinkle yeast and let bloom for 15 minutes.

Make Dough: Mix in sourdough discard, whisk flour and salt, rub in butter, then add yeast mixture until no dry flour remains.

Knead Dough: Turn onto floured surface, knead for 5-10 minutes until smooth, shape into a ball, and let rise in greased bowl covered with cloth until doubled, about 45-60 minutes.

Laminate Dough: Punch down, divide into five pieces, roll each into 8-inch circles, layer with butter, wrap, and chill for 30 minutes.

Shape Rolls: Roll out into 12-inch circle, slice into 12 triangles, make a slit on wide end, roll towards tip to form crescents.

Final Proof: Place on lined baking sheet, cover, and let rise for 30-45 minutes.

Bake: Preheat oven to 350°F (175°C), brush with egg wash, bake for 20-30 minutes until golden brown and hollow when tapped.