Mullins already had six victories in the past 10 years to his name in the race, which was run as a Grade One for several seasons and is now a Grade Two affair.
Easy Game had won a Grade Three over course and distance last month, displaying a smart turn of foot that was again on show.
Settled at the rear, along with Getareason, Ruby Walsh was intent on sticking to the rail, but he was short of room early in the straight, before bursting through to lead at the last.
Getareason had made a move down the outside clear of trouble, looking a real danger, but Easy Game (4-1) knuckled down to win going away in the end by two lengths.
Defi Bleu was sent off the 3-1 favourite but had to settle for third.
Mullins said: “Ruby met with a lot of interference, so it just goes to show how brave the horse is. That’s his sixth run this campaign and his fourth win.
“He’s a horse that has gone a bit under the radar with us. I didn’t dream he would be this successful, and he’s improving all the time. He’s had a tough season for a four-year-old.”
Looking to future plans, Mullins said: “Normally we go from this race to the Lawlor’s race in Naas (Lawlor’s of Naas Novice Hurdle, Grade One on January 6), but this horse has a different profile than previous winners of this race that we’ve had.
“We’ll see how he comes out of this, but he keeps surprising me and getting stronger and better.”
He added of the runner-up: “I was delighted with Getareason. He jumped slow, but he jumped a lot better than he did the last day, and he showed that he’s got an engine.
“He should be up to winning graded races on that run, and maybe he could go further.”
Battleofdoyen cruises home:
Defi Bleu’s trainer Gordon Elliott enjoyed better luck when Battleofdoyen announced himself as a smart prospect with a stylish victory in the Irish Stallion Owners EBF Maiden Hurdle.
Bought for £235,000 after winning a point-to-point, he did not run for well over a year before making a winning debut under rules in a Punchestown bumper last month.
Elliott wasted no time in sending him over hurdles and he jumped with great accuracy for Jack Kennedy, having no trouble in landing cramped odds of 8-15, cruising home 13 lengths clear of Momus, also in the Gigginstown House Stud colours.
“We think he’s a nice horse. He improved a lot from his run the last day in the bumper and he’ll improve again for his first run over hurdles,” said Elliott.
“He jumped very well and a step up in trip the next day will suit him. He stays very well. He’ll probably go to Naas next (for the Lawlor’s race), all being well.”