Chantico is the Aztec goddess of the hearth or something like that. But the drink? Oh, yeah. . .
According to various internet sources, Chantico is a powder containing Sugar, Cocoa (26%) processed with Vanillin, Milk, and Cocoa Butter (also called "White chocolate"). It is mixed with steamed whole milk and served in a diminutive 6 ounce cup.
Basically, it is hot chocolate, so what's the big deal? For one, Starbucks supposedly uses their own source on European Cocoa. Two, Cocoa butter is an ingredient of chocolate, but not generally part of hot cocoa mix. It suppposedly makes it richer. By using whole milk, the whole thing basically takes on the taste and consistency of strong chocolate melted into hot milk.
It is very sweet (a little too much for me) and very chocolately (which is unusual to most palates). It is thick like warm chocolate sauce. If overcooked, it can sometimes be a bit roasted or burnt flavored, but that is usually covered by the intense sweetness.
You can only drink it in small sips, and preferably with some water handy as a chaser. It's either vile or addictive or both. The first time I tried it, I didn't touch it again for months. Now, I can get it about once a week if I have water nearby.