Young was in fine form throughout at Vicarage Road, as he set Manchester United on their way towards victory in the 19th minute with a cool finish.
Former Watford star Young then curled home a brilliant free-kick in the 25th minute after Pogba allowed him to take the set-piece ahead of him.
Anthony Martial made it 3-0, before goals from Troy Deeney and Abdoulaye Doucoure for the home side set up a tense finale.
However, Jesse Lingard made the points secure in the 86th minute with a fine strike, to wrap up the three points for Mourinho’s men.
Mourinho was understandably delighted by Young’s performance on Tuesday night, but he also admitted that he was surprised to see Pogba let him take the free-kick ahead of the Frenchman.
Speaking to BBC Sport after the game, Mourinho said: “I was surprised that Paul Pogba gave him permission [for Young to take the free-kick].”
He continued: “Ashley Young trains at free-kicks and his conversion rate in training is good, so it was good he had the confidence to try it, after scoring the first goal.
“At his age, Young’s playing better than ever and I couldn’t be more happy with him.”
Manchester United’s win lifted them to within five points of Manchester City at the top of the table.
The Red Devils will now prepare for their crunch Premier League clash against Arsenal at The Emirates on Saturday.
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