Cocoa butter sauce for beverages that doesn't resolidify
I think you may be looking for "white chocolate" rather than pure cocoa butter. Cocoa butter doesn't have a huge amount of flavor; it's added to things largely for its texture. At the very least it generally needs sugar and vanilla.

Ghirardelli and Torani both make white chocolate sauces. Is that what you're after? You can make your own by dissolving white chocolate in sweetened condensed milk, which is dense enough that you don't need an emulsifier if you grate it finely and stir.

I'd use this recipe as a starting point. (Omit the coffee powder)
http://www.food.com/recipe/white-chocolate-mocha-syrup-recipe-376916