Don Cossack took full advantage of Champagne Fever's final-fence fall to make it four from four for the season in the Ladbrokes Ireland Kinloch Brae Chase at Thurles.
The Willie Mullins-trained Champagne Fever was the narrow favourite for the mouthwatering clash at 4-5, coming back in distance having failed to get home over three miles when fourth in the King George VI Chase at Kempton on Boxing Day.
Don Cossack, making his first appearance since winning the John Durkan Memorial Punchestown Chase in early December, was a 6-4 shot for Gordon Elliott and Gigginstown House Stud.
Champagne Fever soon adopted his customary pacesetting role under Ruby Walsh and a few extravagant leaps helped him maintain the advantage over his main rival.
The big two began to turn up the heat heading down the back straight the second time, opening up a big gap on the other two runners, Texas Jack and Smokey Joe Joe.
Champagne Fever and Don Cossack went toe to toe at the third fence from the finish and the second-last and approached the final fence almost as one.
Champagne Fever perhaps held a narrow lead when he stumbled on landing and crumpled to the turf, leaving Don Cossack and Bryan Cooper to come home a long way clear.
Walsh and Champagne Fever quickly rose to their feet.
Cooper said: "It was a great race and rode a good race. I thought I had the beating of him (Champagne Fever). He (Don Cossack) missed the second-last, but 20 yards from the last he picked up and rallied and I was quite confident I had the better of him.
"You have to wind him up properly before you go for him and I didn't want to get done for toe by Champagne Fever, so I took Ruby on early as I knew he'd keep going and he did it well.
"He is improving. Because of the size of him he was only a frame of a horse last year and I'm just delighted for Gordon and the team who do a great job with him.
"Hopefully we'll get there (Cheltenham) in one piece."