Mac mini second hdd question

I want to add a second hdd in my 2012 Mac mini and use it as my primary system hdd. I want to keep the current drive in it and use it as additional storage. Can I install the new drive and restore from TM to the new drive and then reformat old hdd after the restore? That would mean I would have two identical drives both with OSX installed at one point. Does anyone know if that will work? Is there another step I should do? Or is it not possible at all. Trying to open up the Mac only once.

Thanks! Any help is appreciated.