Boot into Windows and start an command prompt
or
If your system is not starting anymore start your system with a cd/usb stick and press F10 to get an command prompt

Start diskpart

type list volume and look at the volumes

Select the EFI volume with select volume X (1 in the example screenshot)
This is the volume where your system files are living. This volume is approximately 100MB and of the type FAT32
Assign a drive letter to the volume with assign letter=X

Browse to the assigned volume and open the EFI folder
Here you see a Boot and a Windows partition and possible some Ubuntu, Kali or other distribution subfolder.
Remove all subdirectories except Boot and Windows and remove the assigned driveletter with
remove letter=z