Remove the dough from the freezer one hour before cooking, so that it thaws naturally.
Sprinkle flour on the board, carefully unfold the dough sheet, and stretch a little to thin.
Portion the dough with a sharp, triangular knife.
Put jam at the base of the triangles, roll the croissants lightly towards the top, without squeezing them and place them in the tray in which previously baking paper was placed, a little apart, so that they do not stick when they grow in the oven.
Grease the croissants with a beaten egg and place the tray in the preheated oven at medium to high temperature.
When the croissants have risen and browned nicely, remove the tray from the oven and serve hot. Jam croissants are very good and after they have cooled and can be reheated in the microwave.
Thaw the puff pastry naturally, taken out of the freezer.
If the dough breaks, it can be glued, sprinkled with flour and spread with a rolling pin.
It is good to thin the dough a little, to be sure that it will grow nicely and will not remain raw and unripe.
Use any kind of jam, but the important thing is to be well lowered, so that it is not flowing.
The oven must be preheated and the croissants are baked at high temperature until they grow and brown nicely.