Saw this in the NSW Chatswood store, not sure if it's statewide. The staff didn't know either (how long or if in other stores). A bit of a hack, but works well.
1. Cashback your way to Groupon (currently 5%, can go up during special events)
2. Buy a $20 Ben & Jerry's Groupon - $40 of in-store credit to use on any menu items including any ice cream flavours or a selection of shakes, sundaes & smoothies.
3. Pop in store
4. They have a buy two pints get one free offer going (unknown expiry on this)
5. 4 pints will now cost you a $20 Groupon +$1.85 cash/card ($13.95 x3 (as one is free) = $41.85)
6. Donate one to a fellow OzBargainer who can't make it to Chatswood
Note:
1. You can buy anything else for the remaining credit of $12.10
2. [Edit] Shopback has 15% and another 10% when using code FAST10, until 2000hrs tonight 28/05 (price drops to $18 and $2.70 cashback = total of $15.3 for the Groupon) - Cheers @whitelie
Even cheaper if you have the targeted offer