Advanced users may edit the BIOS binary to inject a custom BIOS logo, modify hidden settings, or replace the Intel Boot Guard components. This requires a clean source file.
This is the hardest step. Official downloads from the original ODM (Original Design Manufacturer) have disappeared from the web. However, here are reliable sources to find your nutmeg-mini-itx rev 1.0 bios bin file: nutmeg-mini-itx rev 1.0 bios bin file