I encountered this idea while randomly browsing an issue of MasterChef magazine in an airport lounge last week during the No Luggage challenge. Junior MasterChef judge said that adding mint was an idea she grabbed from her mother:
Mum likes to point out that she is 'gourmet' because she has always put mint in her Vegemite sandwiches - it's delicious!
Having given it a try, I can confirm it definitely makes the standard Vegemite sanga more interesting. As well as providing added texture, the mint flavour contrasts nicely with the saltiness of the Vegemite. Got your own preferred Vegemite sandwich hack? Tell us in the comments.