Mata received the ball just inside his own 22, weaved his way through several would-be tacklers before producing a magical off-load for James Johnstone to score a wonderful try and send them to a vital win.
It was another excellent European display by the Scots, who had to come from behind after going into the interval 12-8 in arrears following tries from Guilhem Guirado and Facundo Isa.
Darcy Graham scored Edinburgh’s only first half try by finishing brilliantly before Blair Kinghorn took them three points in front at the start of the second period. It was a lead they would not relinquish as a brace of Jaco van der Walt three-pointers and Johnstone’s effort moved them back to the top of Pool 5, despite Julian Savea’s late response.
It should be enough for qualification but they will look to secure a home quarter-final when they face Montpellier at Murrayfield next week.
Following another poor home defeat, the pressure continues to increase on boss Patrice Collazo, with the three-time European champions also struggling in the Top 14, but it was not about the hosts on Saturday evening.
Richard Cockerill’s men have been magnificent in Europe’s top-tier and, despite supposedly being underpowered in comparison to the gargantuan Frenchmen, they played some magnificent rugby.
Although it did not start well, with Collazo’s charges claiming the kick-off and Guirado touching down, the away side hit back superbly and deservedly went over via Graham.
They were opening up the hosts regularly and in Kinghorn the Scotsmen had the game’s most threatening back. He was unfortunate not to see a scything break come to something more tangible in the opening period, but the full-back was rewarded for his endeavour in the second half.
Toulon had regained their lead through Isa’s close range effort but the rangy back three player latched onto Johnstone’s grubber through to cross the whitewash.
That provided them with the momentum they needed and Van der Walt and Johnstone made sure of the victory, even if Savea did go over late on for the former champions.
It was the Welsh region’s first victory in this season’s competition and it came through tries from Rob Evans, who touched down twice, Ken Owens, Johnny McNicholl and Steff Evans.
Dan Jones added four conversions in a good individual display while Leicester’s late consolation efforts were scored via Will Evans and Mike Fitzgerald.