Best way to build the wall if you do not have pour concrete walls to begin with.
They use this method in banks for ATM rooms and ATM lobbies.
Heavy 18 gauge steel studs
Layer of expanded metal mesh
Layer of 3/4 plywood
Layer of 5/8 drywall type X (fire rated)
If you do this on both sides of the and also insulate with Roxul insulation you will not only have a virtually impossible wall to get thru but also fire proof.