To burn a bootloader you need a fully-functioning Arduino or another stand-alone ISP (like USBtinyISP or sim.) You configure the Arduino as an ISP [Arduino as ISP] then you use it as an interface to burn a bootloader to a 328 on another board.
So, your Uno is fully-functional?
Repeating my previous question --
Are you able to upload a sketch to the Uno's micro (328P) when it is parked in the mintduino set-up?