With Old Trafford buoyed by the signing and introduction of Raphael Varane on the pitch before kick-off, the returning fans were treated to an excellent attacking display.
Fernandes and Pogba – aided by a generous Leeds defence – were to the fore, the former benefiting from Pogba's creative talents in opening the scoring on the half-hour mark.
Pogba laid on two further assists for Mason Greenwood and Fernandes to put United in command in the second half after Luke Ayling's screamer had briefly levelled matters.
After Fernandes completed his treble, the former Juventus man teed up Fred to complete the rout in the 68th minute.
Leeds's defending throughout the first half was distinctly haphazard and Illan Meslier had to be alert to turn the ball behind after Pascal Struijk's backpass deflected off Greenwood.
Greenwood was involved again as he slid Pogba through on goal, only for the France midfielder to waste a golden opportunity and fire wide of the near post.
Yet Leeds refused to heed those warnings and Pogba made amends with a superb pass to tee up Fernandes after Meslier punted the ball straight to Scott McTominay, the Portuguese squeaking the ball under the goalkeeper's legs.
For all United's dominance in the first half, it was pegged back three minutes into the second when Ayling left David de Gea with no chance with a vicious right-footed drive from just outside the area.
But Old Trafford was in a stunned silence for just over three minutes as Pogba responded in equally remarkable fashion, his pinpoint long-range pass met by Greenwood, who raced down the left flank and restored the hosts' lead with a strike across the face of goal that went in off the post.
Solskjaer's men then gave themselves breathing room as Pogba made it a hat-trick of assists by finding Fernandes, whose neat turn sent Junior Firpo to the turf and was followed by a composed finish that Ayling could not prevent from crossing the line.
Fernandes' third breached the Leeds goal much more emphatically, Victor Lindelof this time the supplier as United's number 18 latched onto his ball over the top and beat Meslier with an unstoppable volley.
A hugely enjoyable day for the United fans was rounded off by Fred's simple close-range finish and Jadon Sancho coming off the bench to make his debut, Pogba leaving the pitch to a standing ovation after a display that illustrated why signing him to a new contract should be top of the club's to-do list.