Calling Pawn client method on an unpossessed pawn

Here is a pseudocode of how it looks now

void AMyVehicle::ServerPlayerEnterVehicle_Implementation()
{
//do something
Controller->Possess(MyCharacter);
MyCharacter->ClientMethodThatUpdatesUI();
Controller->Possess(MyVehicle);
}

Is there a way to call a client method without AController class taking a possession of AMyCharacter?