I like the idea of single servings, but if you're insistent on buying something with multiple servings, you can do what I do: I put things in plastic baggies or wrap pieces up in plastic wrap. For example, if I buy cookies, I will open the entire package and place the cookies in separate baggies. Like, if I have Oreos, I put 3-4 per baggie and shove the baggies in a container. (I think you're only supposed to eat 2-3 Oreos at a time depending if they're classic or double stuf, though.) Then when you're hungry, you grab a baggie of Oreos and eat them. You may try to go for a second baggie after you finish the first, but if you go for a second baggie, it makes you think, "damn, I just ate a whole bag... which is one serving... I'm not supposed to eat another one." But if you open an entire package of Oreos and start eating them from the package, you don't necessarily realize how much you've eaten until you've eaten the whole thing in one sitting. The idea is to break up the cookies into suggested serving sizes so that you can see how many servings you're actually having. e.g., 3 bags are 3 servings. Sure, using all those baggies is a bit wasteful, but it puts it in perspective for you because you are physically counting the servings with baggies. Most people don't count servings when eating out of the box -- or in your case, the pie tin.

The other thing: sweets are addictive. I've found that the more I avoid sweets, the less I crave them. I'm not saying cut out all sweets from your diet, but you kinda don't wanna touch them after a while of not eating them.