How to recreate Windows Boot Manager ( WBM )

Warning : This solution need to know the bitlocker recovery key of your Windows Drive and to have a USB key with a windows repair system ( Hiren Boot CD or Windows Installation Key )

After unlocking the C: drive of your computer with the bitlocker recovery key open a diskpart in a cmd. 

Select the disk and partition with the WBL ( Most of the time it's a partition of 500Mb with the label "System" ) and delete the partition :

delete partition override

Now time to recreate it :

create partition efi size=500

format quick fs=fat label="System"

assign letter="S"

Now close diskpart and reconfigure the WBM with the commande :

bcdboot C:\Windows /s S: /f UEFI