Alex is very right. If you've recognised it early, then turn around. Since the question never stated "early" you must assume you are in the thick of it.
So what to do?. If you turn around, you'll be in it for the same amount of time it took you to decide to turn around, by that stage, you dead.
At the turn around point you think, "hmmm, ice is bad now, we might be in trouble, lets turn around". Now you have to do the whole journy again!!!
Double the ice you have at the turn around point to give you an idea!.
Even worse is that your lift and stall speed are both xxxxed and you want to initiate a TURN!!!
Best course of action, a bit of power, climb at 1000/1500ft per minute and you'll be up into the "warmer air" in less than 3 minutes. No major control movements needed, no increased G loading, all happy. And you're boss will be slightly happier in that the passengers still get to where they are going.
Nuff said
Steve