I used De Kuyper brand for both the white and dark creme de cacao. Also added a variant with a few drops of chocolate bitters. This is also great with Branca Menta in place of one of the measures of creme de cacao.
I would suggest trying this classic with the addition of a lemon twist (express the oils & discard) along with the nutmeg garnish. I get a sort of lemon meringue vibe on the nose, which really complements and brightens the drink.
Had to substitute white cacao for brown, so cannot make a truly fair review, but I cannot imagine that the true version of this could come anywhere near competing with its delicious herbal-flavoured sister: the BBC