How to create a EFI partition using PowerShell?

I suspect this would be the equivalent in PowerShell:

New-Partition -DiskNumber 0 -Size 100MB -GptType "{c12a7328-f81f-11d2-ba4b-00a0c93ec93b}" -DriveLetter "S"
Format-Volume -FileSystem FAT32 -NewFileSystemLabel "SYSTEM" -DriveLetter "S" -Force

Modify as appropriate to suit your use-case.