Do use a good chocolate that you like the flavor of here; Tcho, Scharffen Berger and Valrhona are all excellent choices.
Malted milk powder can sometimes be found near the ice cream section in markets, I picked mine up in the swoon-worthy bulk section at San Francisco's Rainbow Grocery Co-op
The amount of whiskey I use is relatively small and blends with the flavors of the malted milk; add more if you like, though you may need to add more milk powder as well.
Grate a bit of chocolate over the top with a Microplane.
Nutritional values are based on one of two drinks.