Finally breaking their duck at the third time of asking would be a massive moment for the club both in terms of the celebrations that would follow over the weekend and the boost it would give them ahead of the 2012/13 season.
Victory in the showpiece event at the Twickenham Stoop would not only hand Biarritz a first European trophy, it would also secure a place in next season's Heineken Cup after missing out on that Holy Grail by failing to finish in the first six in the Top 14.
"It's a game with a double goal for us," said Harinordoquy.
"A victory would give us a new title and a ticket for the Heineken Cup next year.
"It would a great reward for our squad, which has suffered this season. It's a huge game with a huge amount at stake and we are going to work as hard as we can to win it.
"It's difficult to say which part of the prize is the bigger reward. We cannot just focus on the title of Amlin Challenge Cup winners - we have to see the full package.
"On the one hand there is a positive pressure in that we could win the title and on the other hand there is a negative pressure because we are playing for the future of Biarritz Olympique. We will therefore do all we can to focus on the title in an attempt to avoid the negative pressure."
Inconsistency has been the byword for Biarritz this season but Harinordoquyis confident his team can turn on the style against Toulon.
Having begun the Top 14 campaign with just one win 10 games, Biarritz travel to London on the back of a 16-5 success over Stade Francais last weekend as they ended their domestic season with six victories in their last eight matches.
"That's the way it is with Biarritz Olympique - we produce the worst and the best!" addedHarinordoquy.
"Right now it seems that we are closer to our best and that's great!
"We were very efficient in defence and showed a good consistency in the scrum and the lineout against Stade Francais.
"Our attack wasn't clinical enough, though. We wasted too many opportunities. We were too excited and we wanted to score too quickly.
"Next week we have to be more patient. We must work on that area of our game, although I prefer it that way as it shows we're working with enthusiastic players.
"For the last few weeks we have been training with smiles on our faces and that's making the difference. We are working in an enthusiastic yet serious atmosphere.
"Friday night is a final. It's a one-off game and anything can happen."