The present paper proposes a methodology for the optimal simultaneous choice of allocation and sizing of Fast Charging Stations for electric vehicles. The methodology is implemented by a Multi-Objective optimization algorithm, based on the Non-dominated Sorting Genetic Algorithm, and by using by using a probabilistic load flow. The optimised planning procedure of two coupled electrical distribution and transportation systems is applied to a case study and the results are presented to demonstrate the feasibility and consistency of the developed models used to implement the method. This approach gives the opportunity to find a proper trade-off between the conflicting interests of different stakeholders, such as the Distribution Network Operator, the Fast Charging Stations owners and the Plug-in Electric Vehicles drivers.