Abbey Lane (16-1) came with a strong late run to claim another big pot for champion trainer Mullins in the Boylesports.com Handicap Hurdle.
Ridden by his nephew Emmet, the eight-year-old jumped into contention at the final flight and battled on stoutly on the run-in to win by two and a half lengths.
Rocky Wednesday was second with the gambled-on 9-2 favourite Ted Veale just behind in third and Joxer fourth.
Mullins said: "He ran right up to his rating last time out at Fairyhouse and I thought he handled that real heavy ground and any time you have horses with a nice handicap mark in a big race like that, worth that sort of money, you've got to take your chance.
"I'll have to have a chat with the owner but maybe we'll have a look at the County Hurdle at Cheltenham."
The winning rider said: "I was wide to stay out of trouble as with 30 runners, things can get a bit messy.
"I knew once I got to the leaders I was always going to outstay them.
"He's a real galloper and he's probably going to be a better chaser next year."