He kicked two late penalties to give Leinster their first lead of the game when it mattered.
The Irish province, who matched Toulouse's four continental triumphs having previously won in 2009, 2011 and 2012, completed their European campaign unbeaten in nine games.
With Maxime Machenaud already sidelined, it was not the full-strength Racing side that boss Laurent Travers would so dearly have wanted in the showpiece as his counterpart instead became the first man to win the title as a player and a coach. "They've got threats all over the park".
"I think they're a side that has come to their peak at the end of the season", he said.
"We had a big heart today, but that's not enough".
All Blacks great Dan Carter is on the bench for Racing 92 with South Africa's Pat Lambie starting at fly-half in the Champions Cup final in Bilbao.
How to Watch Golden Knights vs. Jets
He was among the first coaches hired by the Golden Knights, more than a year before they played their first game. The Capitals were founded in 2001, and play in a 7,000-seat arena to some of the best fan support in the league.
Leinster, boasting a host of players who helped Ireland to the Six Nations Grand Slam this season, came out of their shell on the quarter-hour mark, Jonny Sexton marshalling midfield in waves of attacks.
But Racing 92's hopes of a first European Cup now rest in the hands of French out-half Remi Tales.
With sevens convert Virimi Vakatawa at outside centre, Racing pose a significant threat out wide and Leinster senior coach Stuart Lancaster is wary of their individual ability.
The Top 14 outfit refused to lie down and quickly restored their advantage via the boot of the cool-headed Iribaren, but Leone Nakarawa's deliberate knock-on - for which he was fortunate not to be carded - allowed Sexton to tie the scores on the stroke of half-time.
Racing opened the scoring as Sexton and Iribaren traded penalties with the Irish province finding it hard to settle into the game in the opening 20 minutes.
A well-worked move up the right released Fardy as Leinster sought to hit back and, when Henry Chavancy crept up offside, Isa Nacewa had a chance to level as he took over the kicking from Sexton.