Mix the milk with the yeast and salt and let stand for about 30 minutes.
Put the flour in a bowl and sprinkle the sugar over it. Pour the yeast-milk mixture over it. Let it stand for an hour or two.
After the resting time, knead with the butter to form a smooth dough. Kneading time approx. 15 minutes, correspondingly shorter in the food processor. Let the dough rest until its volume has visibly increased (approx. 1 hour). Fold the dough and let it rest for another hour.
Preheat the oven to 220 ° C (top / bottom heat).
Knead the dough briefly and roll it out into a round sheet of dough. Cut into 12 pieces of cake. Brush the pieces with melted butter and chill briefly so that the butter sets.
Roll up the pieces from the broad side into croissants. Place on a baking sheet (lined with parchment paper). Let rise for another 10-20 minutes. Brush with milk.
Bake in the oven for 15-30 minutes, depending on the oven and the desired tan.
These croissants are also wonderfully suitable for freezing. Just let it thaw overnight and briefly bake in the morning.