To be correct, it is the Chamois Whammy! No matter how you spell it, it is still the same effective nymph or streamer. A good friend of mine, Joe Summers recently retired from Central Piedmont Community College where I worked with him. Joe once told me about a chamois worm that he makes and uses effectively on the Mitchell River in NC.
To make the Shammy Whammy, simply take a piece of chamois and cut it in the shape of an earth worm. I cut it about 1/8 inch wide by about 3 inches long. I keep a couple of these in my tackle box at all times. Since I had not been trout fishing recently, I asked Joe for some pointers and here is his reply. (I hope I am not giving away any of his top secrets.)
I rig the chamois worm by tying it to the leader and adding a small split shot, or weight putty, 4 to 5 inches above. Most of the time I use a strike indicator farther up the leader at the appropriate distance for the depth of the water being fished. Occasionally, I will use a dry fly above as an indicator. ( The problem with this is when you get caught in a tree, you lose two flies instead one.)
The best way to fish the chamois worm is up or across stream and let it drift downstream with the natural flow of the current. Usually fish hit the chamois pretty hard, so strikes are easy to see.
For more information about this type of rig, check out Class 303.