The Portuguese playmaker saved the Red Devils' bacon yet again at Old Trafford, almost single-handedly sending Ruben Amorim's through to the last eight of the competition.
Fernandes could not work his magic to maximum effect in last week's 1-1 first-leg stalemate, but he ran the show at the Theatre of Dreams, firstly netting twice from the spot after Mikel Oyarzabal had sent the visitors ahead.
The former Sporting Lisbon star then finished off a sweeping counter-attack to put Man United in cruise control, before Diogo Dalot rounded off an emphatic evening for the Red Devils.
Leaving with the match ball under his arm, Fernandes also wrote his name into the Europa League history books, setting a new record for the most combined goals and assists in the competition.
Fernandes moves onto 41 Europa League goal involvements
The 30-year-old has now had a direct hand in 41 goals in Europe's second-tier competition - 24 of his own and 17 assists - including four strikes and two helpers from nine appearances in the current campaign.
Fernandes's terrific treble on Thursday came after an equally heroic free kick in the weekend's 1-1 Premier League stalemate with Arsenal, and he has now been involved in a brilliant 28 goals from 43 matches this term.
The midfielder boasts a total of 15 goals and 13 assists from 43 appearances across all competitions, continuing to consistently deliver in the final third in spite of questions and criticism over his attitude and leadership qualities.
Fernandes's efforts on Thursday helped Man United set up an intriguing quarter-final showdown with Lyon, which could precede a semi-final showdown with either Rangers or Athletic Bilbao.
Speaking to TNT Sports at full time, Fernandes hailed the importance of Thursday's win as a confidence-builder for the rest of the season but insisted that he and his teammates must now start to deliver consistent results.
Fernandes reacts to Real Sociedad Europa League win
"This club is all about winning. We need to win games. We have a long way to go, but we are confident if we focus on every game ahead and have the right mentality we can win games," he said.
"With the result and performance when you start to get a bit more confident, confidence is a big thing in football. We are doing very good progress, but the progress will be seen if we get results. At this club it is all about results."
Should Man United get past Lyon and then Rangers/Athletic Bilbao in the semi-final stage, they will clash with either Tottenham Hotpsur, Eintracht Frankfurt, Bodo/Glimt or Lazio in the Bilbao final on May 21.
Amorim's men now turn their attention back to Premier League matters as they prepare to travel to Ruud van Nistelrooy's Leicester City on Sunday evening, aiming to improve on a disappointing 14th-placed ranking in the top-flight table.
Written by
Ben Knapton