What an excellent question.

A few recommendations so far include:

"The Chocolate Box for hot chocolate and Senor Moose (Ballard) for Mexican hot chocolate. The Moose will also make it spicy for you..."

"Hot Chocolate: The Top Pot on Summit is really good. Drinking Chocolate: Oh Chocolate in Madison Valley (across from Nishino)."

"My recommendation for regular hot chocolate is Trophy. They have sipping chocolate too, but their regular stuff is the food of the gods."

This old Stranger piece is another good resource.

Have other suggestions? Speak up!