First, obtain some Vegemite. Planes leave for Australia every day, but there are places in the US that stock the stuff.
Second, defrost a sheet of puff pastry and while you are doing that, get the oven heating to about 400 degrees.
Slather some Vegemite onto the puff pastry. If you are economical with the spread, the taste of Vegemite will be less. Some would say this is a good thing. I prefer lashings of the stuff.
Now add grated cheese. I used Monterey Jack because it was available. Cheddar would be good.
Roll it up.
Cut into slices and place on a greased tray. Bung in pre-heated oven.
When they look done enough, bring them out and start enjoying if you like the taste of Vegemite, or throwing up if you find the taste revolting.