Share 'Toffee troubles'

I'm having trouble with my Toffee recipe (which is as follows); 1 # butter 2 cups sugar 1/2 cup water bring to boil, then turn down heat to medium-high until starts to thicken, then turn on low heat until mixture reaches 295 degrees F., then  pour in pan to cool.   Half of the time, the toffee turns out well.  The other half, the toffee turns dark and tends to separate, and the toffee turns cake-…