One of the reasons is not enough flour, which leads to the fact that the dough turns out to be too liquid and cannot acquire the necessary rigidity. In addition, the cause of stickiness may be the pouring of the dough with a very large amount of sugar, which cannot dissolve in the dough and leads to its liquid. A small amount of fat in the dough can also play a huge role. So don't forget to oil the Madeleine tray a little before use!