We are having granite slabs installed over on new kitchen cabinets. There is a breakfast bar area (made of standard 2 x4/drywall construction). Does the bb slab adhere directly to the cross 2 x4 or should I install hardibacker board (et. Al) prior to granite install? If so, should I use thinset or liquid nails? Thanks in advance.

You don't give any demensions on your bar, but normally granite is siliconed directly to the cabinets.