I often make "BBQ'd ribs" in my pressure cooker from frozen racks of ribs: just stand them in it like frozen boards, literally, (need at least 1/4 c. water in bottom) and pressure cook about 30-45 minutes. Then transfer them to a crockpot or baking pan, cover all sides with BBQ sauce (pre-warmed if you're in a hurry) and get hot; serve like they'd been cooking all day. Only thing is, I often cook them until the bones slip out so sometimes I just start with the boneless pork 'country style spareribs' to begin with.