In a container, mix the water with the lukewarm milk, 1 teaspoon of sugar and the dry yeast, mix and leave for 10 minutes to activate.
In a large bowl, mix the sifted flour with the salt and remaining sugar.
Pour in the already activated yeast.
Incorporate the ingredients together then add 100 grams of butter at room temperature, mix then knead until the dough no longer sticks to your fingers.
Shape the dough into a rectangular form, wrap it with cling film, and refrigerate for at least 4 hours.
On a baking sheet, add 250 grams of butter and gently spread it into a 20x20 cm square shape, using a rolling pin.
Put it in the refrigerator.
Take out the dough with the butter 10 minutes before starting to work.
Sprinkle the work surface with flour, add the dough, sprinkle with flour again and roll out with a rolling pin into a 50x 25 cm rectangular shape.
Add the butter to one edge and cover with the other side, lightly press the edges, sprinkle with flour, and gently stretch the dough lengthwise only.
Now again, fold 1/3 of the dough towards the middle and the other 2/3 to the opposite side, then fold the dough in half once more,
Cover the dough with baking paper and refrigerate for 60 minutes.
Turn the dough out onto a floured work surface, roll it out into a rectangle again and fold it over, cover the dough with baking paper and refrigerate for another 60 minutes.
Sprinkle the surface and dough with flour, roll out again into a rectangular shape until it reaches a thickness of 4-5 mm.
Cut a triangle with a width of 8 cm.
Roll the croissants, and at the end, gently round off the edges.
Transfer the croissants to a tray lined with baking paper.
Cover with cling film and let rise for 90 minutes.
Brush the croissants with beaten egg.
Bake in a preheated oven at 200 °C for 10 minutes.
Reduce the temperature to 185 C and bake for another 10-12 minutes.
