The Sheffield fighter was far too good for his challenger at the O2 Arena, stopping the former amateur ace in the sixth, and afterwards revealed he had struggled to motivate himself for the bout.
Brook says he should be in the ring with the division???s big names and criticised fellow Brit Khan for refusing to agree to a fight.
???There are many more things to come from me,??? Brook told Sky Sports.
???In the dressing room I said, ???my adrenaline???s not running???. I wasn???t excited. But I thought ???it???s a big show, I???ve got to go out and perform???.
???I want big, big fights now.
???As for Khan, it???s getting boring now. We???ve offered him, we???ve asked him to pick a phone up and talk but he don???t want to hear.
???I???ve got this title, I???m in the welterweight division ??? why not come and fight me? This guy here (Gavin) has got the cojones to come and fight me. I take my hat off to Gavin.???
As for the contest, Brook said he enjoyed testing his boxing skills against former world amateur champion Gavin, but always knew he would have the power to end the contest.
???I always knew he???d be tricky and I knew it would be scrappy,??? said Brook. ???He???s very awkward, crafty and smart in the ring. I knew it would be tricky for a few rounds. But I knew it was just a matter of time before I nailed him.
???He won the worlds in the amateurs, so I was testing my skills against him. He???s a very talented boxer.
???We could see Frankie was tiring with the heavy-handed shots I was catching him with and it was just a matter of time. I came up with a good shot and I capitalised on it.???