Remove the peel from the onions and cut them into fine rings. Bring water (1) to a boil, add onions and cook over high heat for fifteen minutes. Drain, drain and set aside.
In a frying pan, make water (2) and sugar until sugar is completely dissolved. Add onions and apple juice. From the point of boiling again, make on high heat for about ten minutes. Stir from time to time, the onions should not stick to the bottom! Cut the truffle into small cubes. Add only at the end of the cooking time. Immediately fill into hot jars. If you decide to use morels or dead trumpets, soak them in warm water for about twenty minutes, rinse well and cut off.
Also add them only at the end of the cooking time.