Ludovic Mercier delivered a master-class performance as Pau overpowered Brive 37-16 to take a major step towards the European Challenge Cup final.
The former Gloucester outside-half helped himself to a 27-point haul, including a crucial second-half try, to give the 2000 Cup winners a major advantage over their local rivals.
Brive, who have accounted for Saracens and Worcester in this competition, took the lead when France wing Julien Laharrague went over on 15 minutes.
But Mercier, who booked Pau's place in the last four with a last-gasp penalty against Clermont-Auvergne in the previous round, booted four penalties before converting Mathieu Dourthe's timely try just before half- time.
Brive scrum-half Valentin Courrent kept his side in touch with a series of penalties after Pau were temporarily reduced to 14 men until Mercier completed his full-house of scores by racing onto his own kick to score ten minutes from time.
Nicolas Martin crossed in the final minute to give Pau a commanding 21-point lead for the second leg at Brive in less than three weeks' time for the right to face either Sale Sharks or Connacht in the final.
