Sean Dyche was denied the chance to celebrate his 100th game as a Premier League manager with a win as Manchester United ground out a narrow victory through Anthony Martial’s second-half strike.
One again the Burnley boss saw his side compete with one of the division’s heavyweights as they continue to test the best the top tier has to offer.
But United’s one moment of class in a performance that matched the colour of their grey shirts for steel, rather than flair, was enough to give Mourinho’s side the victory that still keeps them as nominal title challengers.
Martial coolly slotted home the first of only two efforts on target from the visitors, who were then pushed all the way by the Clarets but had the nous - and the spoiling tactics - to help David De Gea keep a fifth successive clean sheet and a 14th in the league this season to safeguard the points.
Turf Moor remembered the Burnley supporters who passed away in 2017 and former England striker Cyrille Regis following his death at the age of 59
Dyche had also faced Mourinho in his first top-flight match as manager when the Portuguese was in charge at Chelsea at the start of another title-winning campaign.
He is yet to repeat the trick with United and his side’s slim hopes of catching Manchester City at the top of the table could ill afford a setback at Turf Moor.
History was on their side, with the Clarets having won only one of the previous 24 meetings between the two clubs.
But Dyche’s side was only minutes away from improving that record on Boxing Day when an injury-time equaliser from Jesse Lingard denied the Clarets all three points.
That was the last time De Gea had conceded a goal when he was beaten by Steven Defour's epic free-kick, and again United were pushed all the way as this Burnley side looked to mirror the achievement of the class of 2009 who beat the then-champions to record a first Premier League victory.
Robbie Blake’s famous winner still gave him the status as the only Burnley player to score against United in nine visits to Turf Moor.
But he was almost joined at the 10th attempt on a number of occasions during a first half in which the Clarets again more than matched their big-spending visitors.
James Tarkowski – a United supporter as a boy – headed wide an early free-kick from Johann Berg Gudmundsson, with defensive partner Ben Mee doing likewise from a Gudmundsson corner later in the half.
Gudmundsson tested De Gea, but not with sufficient power to trouble the United keeper following an excellent counter-attacking move.
And it also took a fine tackle from England defender Phil Jones to stop Ashley Barnes pulling the trigger after the fit-again Scott Arfield, whose return was the only change to Burnley’s starting line-up, and the impressive Jeff Hendrick worked the opening.
United, unbeaten in their last seven games, got little joy out of the Clarets’ defence at the other end, Paul Pogba lifting an effort over the top and Ashley Young curling a shot just wide two minutes before the break from their best opening.
But like most of the top teams, United needed just one chance to make the difference and nine minutes after the break they went in front – seemingly from nothing.
Romelu Lukaku’s show of strength on half-way allowed him to break clear and pick out Martial with a sweeping pass and the finish from the France international was top-class as he steered a shot into the top corner for his 11th goal of the season.
The visitors took an eternity before Burnley were able to re-start the contest and then used every opportunity to run down the clock as they looked to prevent Dyche's men from building any sustained momentum.
But the Clarets responded superbly to the setback as they looked find an equaliser and keep alive the hope of a first win in seven league games.
A free-kick just outside the penalty area gave Defour the chance to reprise his moment of magic at Old Trafford. But this time it was Gudmundsson who took responsibility and the Icelander was unlucky to see his effort clip the top of the crossbar.
The Clarets’ winger was instrumental in most of the Clarets’ most threatening moments and after seeing a goalbound header blocked by Chris Smalling he then sent a low cross skidding across the face of goal, with Tarkowski just unable to get a touch following a deflection off Smalling.
With 10 minutes to go, Dyche sent on on-loan winger GK Nkoudou and Sam Vokes to try and add an extra cutting edge and the move almost paid off.
Nkoudou's extra pace stretched the visitors' defence, while Vokes immediately provided an aerial threat as United were forced to defend in numbers and play on the counter-attack, Nick Pope saving from Martial to keep the Clarets in the hunt.
Dyche’s men gave absolutely everything to try and get some reward for their efforts and after Vokes had nodded wide under pressure even threw Pope forward for an injury-time corner.
But they couldn’t find a way through - drawing a blank in front of goal for the third time in four league games - as United grimly hung on to a victory where the value was in the points not the performance.
Burnley: Pope, Bardsley, Tarkowski, Mee, Taylor, Gudmundsson, Cork, Defour, Arfield (Nkoudou 81), Hendrick (Vokes 81), Barnes (Wells 89). Substitutes: Lindegaard, Lowton, Westwood, Long.
Booked: Mee, Bardsley
Manchester United: De Gea, Valencia, Smalling, Jones, Young, Pogba, Matic, Lingard (Rashford 79), Mata (Fellaini 72), Martial (Herrera 90+3), Lukaku. Substitutes: Romero, Rojo, Shaw, McTominay.
Booked: Pogba, Matic, Rashford.
Referee: Mike Dean