First, I like to work with fair trade organic cacao nibs. Spread them in a thin layer and toast lightly at 350˚F until they start to darken and sizzle. Then, after they've cooled just slightly, add them to the Vitamix. You may be able to do this with another blender, but the ultra slow speed option of the Vitamix makes the process very easy.
Blend on low until a thick paste forms. Then add a bit of non-dairy milk - just enough to loosen the cacao so it can be easily blended. I like almond milk best for this beverage. Increase the blender speed to the highest setting. In a high powered blender, the friction of the blade will cause the mixture to heat up. Continue blending until the mixture reaches ~150˚F, adding milk as needed to keep the entire mixture available to the blades.
When heated, and smooth, add a bit of vanilla bean and cayenne pepper (if you like things wild). Unless you're using a sweetened milk, it may need sweetening at this point, too. Blend a while longer to ensure that all the ingredients are completely mixed through.
To ensure consistency, be sure to strain the mix through a very fine sieve. Pour up the mixture and garnish with flake salt. I like Maldon or a fleur de sel.