I would guess (though no science here) that the butter may be the culprit. I always use melting tabs or almond bark. I thin it with a bit of lard. I have made it with ghiradelli and also with choc. chips, the result being a chocolate that takes forever to harden and softens up easily, but always adheres.
Your results are confusing to me. (and a bit magical too, I might add).
Jo

Are you putting powdered sugar oin yout short breads before dipping?
I have successfully dipped biscotti in just melted Ghiardelli chips.
Linda C

I use semi-sweet Ghiradelli blocks from Trader Joe melted over simmering water. I dip biscotti as a rule. If my cookies have to be shipped I add a bit of paraffin. Other people use a bit of Crisco. Maybe your shortbread needs to be dusted? The only thing I can think is that a fine coating of flour on the surface is keeping the chocolate from sticking. Try dusting them with a dry pastry brush. Otherwise I'm clueless.

I can't offer any advice, but I feel your pain. I tried dipping biscotti in meted Ghiardelli white chocolate chips last year, and it would not stick, even after the melted chocolate cooled. It was too greasy, and I didn't even add butter or anything. Next time I make that recipe I'm just going to include some of the chips in the batter.

I have not put any flour or sugar on the shorbread before dipping. I might add that when I have spread some choc on top of the shorbread, if I turned it right over, the choc would have fallen off. it happened on one of the earliest batches, so I learned That Lesson.

btw, why crisco not butter?

You can also dust with cornstarch or rice flour or a combo of both before dipping in chocolate.

But I had problems with Ghiardelli, dark and white, chocolate. The dark Ghiardelli covered but not as well as the hersey's but the white hardly covered at all and was just plain weird. I added some Hersey's white to the white Ghiardelli and then it was fine. Also the white Ghiadelli discolored a bit although it was in the double boiler and did not scorch or burn.

Michelle

Butter has some water in it I think. For thinning chocolate a bit I have usually used oil. But for dipping I usually use the chocolate without adding anything.

I suspect also that whatever they use in the chips to keep them firm during baking is causing the problem, at least partly.
I use good eating semi-sweet chocolate melted with nothing added, never have any problems.

I always avoid butter because the water content will cause it to seize and become a lumpy mess. Oil or lard will work fine to give it a glossier finish and easier dipping.

Jo

I guess I just have to go to TJs and get that 10lb bar of chocolate!

Maureen the last shortbread I dipped (2 weeks ago) I used the pound and a half of bittersweet from TJ's..no added anything..even melted in the micro.

I dip a lot of Buckeyes every so often. This time, I put a heating pad in a large stainless steel bowl, put a towel over it (so it wouldn't get messy), then set my glass bowl of microwave-melted chocolate chips on top of the pad. The chocolate stayed a nice melty consistency - didn't start to "drag."

(I actually can't take credit for this, though; I saw it on TV - America's Test Kitchen, maybe?)

I never add extra fat to the chips and I also nuke them first. I used to put the Buckeyes in the fridge to set the chocolate, but have found that they're better if they "cure" at room temp.

On Food and Cooking mentions using clarified butter mixed into chocolate - if you really want to use butter, clarifying it first might remove the water issue.

I don't do much dipping (although I've been known to spin my partner pretty good) but from what I read here, it doesn't seem to be a matter of water, butter or any oil but rather a matter of the type of chocolate.

I've melted lots of chocolates and their characteristics are so variable and so unpredictable (from type/brand to type/brand).

It looks like some good chefs here have found chocolates that do what they hope they will do.

Joe