I got this from Cooking Pleasures magazine and it is amazing. I modified it a little bit, but not much--I beg you to eat this.
1 1/3 C sugar
1 (7 oz) jar marshmallow cream (fluff) (I make my own fluff--it is much cheaper and tastier than the storebought stuff. Just google homemade marshmallow fluff)
2/3 C evaporated milk
1/4 C butter
1/4 t salt
1/4 C lemon juice
12 oz bittersweet chocolate (the original recipe used semi-sweet)
6 oz semi-sweet chocolate (the original recipe used milk)
1 T lemon zest
(The original recipe used 1 t lemon extract, but I chose to omit this because I don't like the fakey taste)
Line 8" square pan with foil, folding excess over sides for handles
Combine sugar, fluff, milk, butter, salt in large saucepan over med heat until melted, stirring occassionally
Increase to med-high heat and add lemon juice. Bring to a fast boil; boil for 5 minutes or until temp reaches 212 degrees, stirring constantly. Remove from heat.
Stir in chocolate, until melted. Stir in zest. Pour into pan and refrigerate overnight or until firm