Steffensen found himself on both the right and wrong side of a late drama in each of the two races, starting with a somewhat fortunate win in the opener.
He had spent the majority of the race well behind Dan Reardon, the motocross ace bolting from pole and swiftly building a lead of over five seconds.
However Reardon struck trouble three laps from home, DJ Carl Cox sending the leader into a spin on Mountain Straight while being lapped.
That gifted the victory to Steffensen, his winning margin a healthy 10s over Supercross legend Chad Reed.
Reardon, meanwhile, was dumped back to fourth by the Cox contact, but did manage to get back on the podium after passing Greg Murphy at The Chase on the penultimate lap.
He then almost chase down Reed, the pair only split by a couple of tenths at the line.
Mick Doohan finished fourth despite a mid-race clash with Zak Brown. The McLaren boss had been running a relatively comfortable third, only to be tagged by an out-of-control Doohan at Murray's Corner. Once going they rubbed panels again down the front straight, running Erebus boss Barry Ryan wide in the process.
Doohan recovered best, with Brown and Ryan dropping behind Craig Lowndes.
As expected there was plenty of drama at the early stages of the reverse grid race.
At first it seemed Reardon had fared best of the front-runners, getting as high as fifth on the first lap before the Safety Car was called to calm things down. However he was taken out during the caution and dumped to the back of the field.
That left Steffensen well-placed for a clean sweep, the Race 1 winner well within striking distance of pole-sitter Scott Pedder with a couple of laps to go.
However an unforced error at Hell Corner on the final lap cost him a second win, Pedder able to cruise to a 7s win over Blake Williams and Brad Hodge.
Steve Richards and Doohan were next, with Steffensen dropping back to sixth.
Reardon was only able to recover to 10th.