Jen, I think you would want the best chocolate you can find thats with in budget but I would think Nestles would be fine, I use it for most everything. The cheaper the choc. the more filler oils and the like which you dont want. Yes, work fast and put the choc pieces right on the hot toffee....give it a few minutes to melt, then spread gently. I just wanted to tell you too that the chips will still hold thier shape and look like they are Not melting....THEY ARE and after a few minutes they are so soft you CAN spread them.....
I actually googled "chocolate falling off toffee" after reading your post....just to make sure I wasnt making a mistake.....several people mentioned the same thing. Others said it may have to do with microwaving the choc so Im not sure about that theory. I no longer make toffee...to many burns LOL but I love it.
This year its the simple ole Jiffy super easy fudge, I bought a bunch,about 50 little plastic red and green Christmas tree shaped trays last yr. after the holidays...I think they were a nickle. I just poured the fudge right in the little containers, covered each with a little celo and a ribbon......so easy....no cutting or packaging B/C it comes in its own little package each hold about 1/2 lb fudge.
What other goodies are you making?
Sorry, I forgot to answer your other ?....yes semi sweet or sweet or dark...thats all just a matter of personal taste. I think they suggest semi sweet so that its not OVERLY sweet. Funny but the new rage in chocolate is adding black pepper, cyanne pepper and red pepper...to make it more of a savory flavor. Im not sure if Im brave enough to make a black pepper chocolate fudge yet LOL....but my hubby wants me to try buffalo fudge with hot sauce...Not happening here!!