I can usually win pre-6 because his silence doesn't last long enough yet to stop me from frostbiting while he's still chilled from flash frost, but once he gets riftwalk, unless he's just bad, it's over for me and I have to hug the turret. The cooldown is so low that he can do it every time I throw a q, and his silence interrupts glacial storm so I can't trap him into flashing into me, and once he hits 10 or 11, the silence outlasts my flash frost's chill effect so I can't even frostbite him anymore...advice?

get blue buff push down his tower..he's kass he will roam sometimes. when he does kill the lane. If you need to do a frost bite nuke use a quick tick of r. Kass can't handle heavy tower pushes without blowing threw tons of mana. Theres not real reason to try to drop a q on him unless you need the stun.

Like other champs that have CC based on a skill-shot, use it aggressively pre-6, and then afterwards you need to save it. Kassadin doesn't have much sustain or staying power, so if you can force him out of lane to get a minion/exp advantage, do it.

As I said in the thread about the person asking about Ahri tips, Kassadin can restore mana but only when he autoattacks minions. If he's low on mana, harass him and don't let him near them. This will stop his inflow of extra mana, pacing the game to your needs.

After 6, save your Q for when he jumps at you. Like Yi or Pantheon, when Kassadin jumps at you, it's a clear indicator of where he's going to end up since he wants to be relatively near you. Fire and quick detonate for the stun, flash frost, and go to town on him-- or use the stun to get away.

At low levels, Kass won't really be able to DPS through your egg form easily, not without jungler / tons of minions helping. Feel free to be a little more aggressive than usual, but don't forget to be aware of ganks and mia's.

You're not going to kill him or even stand much chance at counter-harassing, your goal at is to 1) not die 2) outfarm and 3) prevent him from roaming. If you can keep him in lane instead of ganking top/bot and force him to try and kill minions at his tower by clearing waves with R+Q, he'll end up underfarmed and you'll be a lot more useful once teamfights start. If he leaves lane to gank, take his tower.