Do I need to buy additionally the 'cork'...
Do I need to buy additionally the 'cork' or just the fuel bottle, such as this: http://www.backcountry.com/msr-fuel-bottles?
You'll just need the fuel bottle if you want to use liquid fuel.
If you plan on using propane only then you don't. If you're planning on using white gas/liquid fuel then you'll need the bottle.