Popcorn proved too strong for Rathlin as the two fought out the finish of the opening beginners chase at Thurles.
The pair moved on from front-runner Sizing Santiago four from home and were upsides jumping the second last.
11/4 shot Popcorn got the cleaner jump at the final fence, under Patrick Mullins, and powered home to the line to record a five-and-a-half length victory.
The runner-up was the one for money (7/4 into 11/8) but failed to jump with fluency and had to settle for second best.
The winner had been successful over hurdles here last season and was making a perfect start to his chasing career.
Trainer Willie Mullins had recorded three victories at Fairyhouse yesterday and was saddling his fourth winner in a row here:-
"Patrick said he could be the type for the four-miler at Cheltenham. He's a very natural jumper and you wouldn't mind sending him anywhere.
"After today he could even do something over a shorter trip."
