Milan edge out Bologna at home
The Italy international orchestrated the Rossoneri's first win of the season with a hat-trick at the Renato Dall'Ara back in September, but he had laughed off suggestions he could repeat the trick at the San Siro.
There was a touch of fortune about his opener deep into the second half, but his second goal was borne of fantastic individual skill and a predatory instinct in front of goal.
Philippe Mexes gave the hosts cause for concern with a careless own goal in the final stages but a rejuvenated Milan side found themselves back in the race for Europe.
After his lacklustre display at Sampdoria, Stephan El Shaarawy was keen to get back among the goals, his 13th-minute effort only thwarted by the trailing leg of Federico Agliardi.
M'Baye Niang then burst free down the right to spin a low cross into the box but no Rossoneri shirt was there to tuck the ball into an empty net.
Agliardi saved Bologna again, pushing Pazzini's header out for a corner following fine work from Kevin Constant.
Milan goalkeeper Cristian Abbiati, conversely, would have a quiet first half and he telegraphed Alessandro Diamanti's speculative drive from distance.
Niang has impressed during an extended spell in the first team and his defence-splitting ball to Constant had Bologna's defence on their toes five minutes before the break.
The hosts spurned two chances to take the lead going into the interval as Agliardi cleared Pazzini's header as far as El Shaarawy, the Bologna keeper then managing to parry the young striker's snapshot to safety.
There were no changes in personnel or tactical approach from either side as play resumed, and Milan continued to probe the same avenues that had proved fruitless in the first half.
Niang found space to test Agliardi with a weak left-footed attempt from distance, the Bologna keeper smothering, and a triangular move involving El Shaarawy and Pazzini soon ran out of steam.
Ignazio Abate stepped up from the defence to assist the frontline in the 58th minute, his low ball into Pazzini resulting in a shot against the near post.
The near miss breathed new life into Milan and Abete continued to rally his team-mates with a fine dribble into the area that won a corner.
Pazzini steamed into the area to strike the incoming ball on the volley, Mikael Antonsson's heavy deflection wrong-footing Agliardi as Milan took the lead.
Bologna threatened a prompt response, Riccardo Montolivo stepping in to deny Diamanti a free shot on goal before Constant got across to block a firm drive from the ex-West Ham striker.
As the final 10 minutes approached, there was still time for Pazzini to continue his torment of Bologna and his deft touch, flick and finish was truly remarkable.
Mexes had less reason to be cheerful four minutes later when he haplessly nodded substitute Cristian Pasquato's tame shot into his own net.
Four minutes of stoppage time made for a nervous finale for Milan, but midfielder Montolivo tracked back to cut out one last Diamanti drive to see the Rossoneri safely home.