Mix and ferment sourdough for 3 hours with 86°F. Then add other products to sourdough and knead the soft dough. Ferment the dough for 2 hours with 80°F, punching it twice.
Divide the ripe dough by 3-4 pieces, roll each piece in a circle.
Initially divide each circle by 4 parts, then half each part. You may divide as many times as you want, depending on the size of croissants you want.
Place jam in every part.
Roll every par, shaping it as a croissant. Place all the croissants in an oiled baking paper. Leave it to proof for 86-113°F then lubricate by the egg.
Bake in the oven preheat to 392-428°F for 30 minutes or to ruddy crust.