Un Atout was cut to 16-1 for the Supreme Novices' Hurdle by Paddy Power after an effortless debut victory over timber in the Kells Maiden Hurdle at Navan.
A wide-margin winner of his only bumper, he runs in the Gigginstown House Stud colours and Davy Russell set out to be positive on the four-year-old, leading all the way.
Useful rivals Some Article and Fickle Fortune closed up, but Un Atout (1-2 favourite) kicked clear of the latter to win by four and three-quarter lengths, coasting over the line without ever being threatened.
"We knew he would probably have to make the running, but he was brave in front to go and make it first time over hurdles," said Mullins
"He jumped like a chaser early on, but his jumping flattened out as he sped up. He's probably more of a stayer and he's a chaser for the future. We'll see how he comes out of this and we'll definitely have a look at Christmas. He'll be entered in all the top novice races."
Moscow Mannon, fourth in last season's Cheltenham Champion Bumper, made a stylish winning debut over jumps in the Irish Stallion Owners EBF Maiden Hurdle.
A triple bumper winner, Brian Hamilton's six-year-old made the transition to obstacles with the minimum of fuss as he set about the opposition.
Always in command, he was never seriously threatened as he swept to victory under Andrew Lynch by two and three-quarter lengths from the Mullins-trained The Paparrazi Kid.
Hamilton said: "I'm glad to get that out of the way and I can relax a bit now. I doubt he'll go to Leopardstown as he pulled muscles six or seven weeks ago which messed us up a bit. Leopardstown may come a bit quick.
"He'll probably go for the Slaney Hurdle (over two and a half miles) at Naas (January 6). We'll step him up a bit and that's the idea at the minute. He should improve quite a bit from that run."