Paddy Butler helped Pau to a pulsating 38-33 Challenge Cup defeat of Zebre in Italy on Saturday.
The visitors scored three tries in 13 minutes to turn the game on its head at Stadio Lanfranchi and make it two wins from two in Pool 3.
The hosts were 30-7 ahead at the break but Pau stormed back, with Peter Saili crossing and Zebre coughing up two penalty tries in five minutes. Tom Taylor's penalty and another try from Lekima Tagitagivalu completed the comeback, and backed up the opening win against Gloucester.
Former Munster second row Dave Foley was not in the Pau matchday squad.
It was an unhappy return to Irish soil for Donncha O’Callaghan as Worcester Warriors fell to a 15-8 Challenge Cup loss against Connacht.
O'Callaghan replaced Pierce Phillips with 15 minutes to go but couldn't stop the Westerners digging out their second pool win, as tries from Eoghan Masterson and Matt Healy decisive.
Peter Stringer was not included in the Warriors squad for the trip.
Former Ulster lock Dan Tuohy featured from the bench as Leicester Tigers ran in seven tries in a 54-29 Champions Cup slaying of Castres.
Twinkle-toed wing Telusa Veainu bagged a hat-trick in a Tigers mauling at Welford Road. That sent them top of Pool 4 after they picked up a losing bonus in last week's loss against Racing 92.
Marty Moore played the final 22 minutes of Wasps' 41-10 bonus-point destruction of Harlequins.
Nathan Hughes terrorised Quins as the hosts swept aside their Premiership rivals in the Champions Cup collision in Coventry.
The England number eight spearheaded Wasps' five-try assault on Quins as Dai Young's men ended a miserable run of five straight defeats in style at the Ricoh Arena.
Harlequins centre Francis Saili suffered a nasty-looking injury late on, carried from the field on a stretcher following lengthy treatment owing to a head-first collision with Joe Launchbury's hip in a miscued tackle.