Theobromine is fatal to both dogs and cats.  If you simply have to feed them "chocolate" then get them carob, which has no theobromine.

It doesn't matter whether or not they "like" it, if they get enough theobromine in their system, there is no going back, you will have a dead animal.  Not all alkaloids are poisonous to cats and/or dogs, but that one is very well known.

My sister's cat used to love cabbage.  That cat would run to the fridge if anyone even said the word "cabbage."  She would then sit patiently by the fridge until someone gave her a big piece of cabbage, which she would then nibble on for an hour or so until it was allllllll gone.

Could be worse, could be raining.