[{quoted}](name=venomous frost,realm=EUW,application-id=3ErqAdtq,discussion-id=Eu0NUTR3,comment-id=0000,timestamp=2016-06-13T20:18:18.809+0000)
poke him down to where his maw passive procs, all in him when the passive is down, NEVER fight him when it's up, you just won't win.
that being said, most AP mages just straight up lose vs maw users that can close the gap on you.
Venomous Frost had good things to say, I just want to expand on a few things.
First situation, If you lost to your laner before they got their Maw of Mal, then the better option is not to duel them especially when they have maw. You can Poke, but make sure you're still wave clearing, and roam if your champ is good at that, if you're good at non of that, turret hug wave clear.
Second situation, you beat your laner before they got Maw of Mal. Try and use the method you used to beat them, and don't over commit to killing them, a recall, and wave clear is good enough. Now, if you lost to your laner, go to (First Situation.)
Hope this helps! :)