Edinson Cavani marked his return from his Paris Saint-Germain exile with a goal as the Ligue 1 champions came from behind to beat Evian 4-2.
Cavani and Ezequiel Lavezzi were named in Blanc's squad for the first time in 2015 after being omitted from the last three games for missing a mid-season training camp.
And the Uruguay striker repaid the faith shown in him by the under-pressure PSG coach by putting the finishing touches his side's first league win of the year.
Blanc - who saw PSG throw away a two-goal lead at Bastia in a 4-2 loss last weekend - must have feared the worst when Cedric Barbosa put lowly Evian ahead in the 14th minute.
David Luiz levelled on the half-hour mark and Marco Verratti gave PSG the lead six minutes later, only for a Gregory van der Wiel own goal just after the hour to leave the hosts on the brink of dropping more points in their pursuit of table-topping Lyon.
However, Pastore popped up to coolly steer home a pull back from Lucas Moura before substitute Cavani tapped in a fourth a minute from time to move PSG back to within four points of Lyon. Evian, meanwhile, remain 18th.
PSG offered little going forward early on and were punished for a defensive lapse by a fine strike from Barbosa.
The hosts conceded possession from a throw-in deep inside their own half and Barbosa duly took advantage with a volley into the bottom-left corner from the edge of the area.
Blanc's men were wasteful in possession for much of the first half, and when they did find their rhythm, they were repeatedly denied by Benjamin Leroy.
The Evian goalkeeper produced a brilliant reaction save to keep out David Luiz's close-range effort and then did just enough to turn a Zlatan Ibrahimovic shot around the post following great work down the left from Blaise Matuidi.
Leroy came to the rescue again to palm a Lucas drive over, but his resistance was finally broken from the resulting corner - the stopper unable to keep David Luiz's near-post header out despite getting two hands to the ball.
Evian would have retaken the lead had Barbosa not fired wide at the end of a rapid counter soon after. And the visitors were quickly punished for Barbosa's profligacy when Verratti powered home from 10 yards following Evian's failure to clear a Lucas free-kick.
A scrappy second half was light on goalscoring opportunities but Van der Wiel gifted Evian a route back into the game. The Netherlands international headed Daniel Wass' right-wing free-kick under the legs of goalkeeper Salvatore Sirigu.
Ibrahimovic latched on to a Pastore flick-on as PSG sought an immediate reply, only for Leroy to divert the Swede's effort off target.
Cavani was thrown into the fray to aid PSG's cause, yet it was Pastore that provided the crucial contribution with a well-taken finish in the 74th minute to lift some of the pressure on Blanc.
And there was still time to Cavani to apply the gloss to an unconvincing PSG display, turning home Ibrahimovic's cross-cum shot from point-blank range.
