Why do my caramels turn out hard in the center? I have made several batches of homemade caramels, and they have all turned out the same - soft around the edge of the 9x13 pan I use to cool them and hard as a rock in the center of the pan.  Seriously, the caramels at the sides are soft and chewy, but the ones in the center are so hard that if they're bent at all, they crack (with a cracking noise).
I have noted that the part that is hard is also the part over the area on that pan where the caramels are first poured out. Coupled with this, the top of the entire pan of caramels is slightly crunchy.  There is no discernible grain to them and they look and taste like they should (except for the center caramels, which is like a really grainy toffee).  Of course, the recipe is from my mom, who manages to make them without any problems -sigh-
Anyone have any ideas about what I'm doing wrong??  Thanks for your help!
Here's the recipe I use: (I do not deviate from this, at all)


2 c. superfine sugar
3/4 c. light corn syrup
1/2 c. butter
2 c. whipping cream

Boil all ingredients except for 1 c. of cream over medium-high heat, stirring constantly.  Stir in remaining cream.  Reduce heat and stir occasionally, until candy reaches 240°.  Take off heat, stir well, and pour into buttered pan.  Cool completely before cutting.
The higher the temperature, the harder the caramel. That is basically the whole story. So I think what is happening to you is that the caramel in the middle is still going up in temperature due to residual heat, while the stuff at the sides cools down quickly because it can vent heat through the pan to the outside world. Have you checked the calibration on your thermometer? In any case, I think the things you can try are (1) cook to a slightly lower final temperature (back down a couple degrees at a time) and (2) set the pan over a tray of ice to cool it more evenly. Also, be sure to do a really good job of that final stir before pouring into the tray.