It is possible to obtain two PhD degrees (various fields) on the basis of one interdisciplinary PhD dissertation?
No, at least the regulations that I am aware of require that the dissertation be a novel contribution to the respective field and that it has not been submitted before.

If you write a dissertation at the crossroads of different fields, you have to decide for a field in which you want to formally graduate and obtain a degree. It may be advisable to look for supervisors from different fields or with an interdisciplinary background.