Suggestions for caramel from dark brown (muscovado) sugar? I'm thinking about making caramels for holiday treats, and as some of the flavors I'm considering are quite intense (and for variety's sake), I'm considering trying to use a much darker, richer sugar.  Previously when I've tried doing caramel with brown sugar, the molasses seemed to lead to a rather intense foaming and an astonishingly un-appetizing result; I'm wondering if there are any specific tips folks can offer for getting brown sugar to behave reasonably well while I'm caramelizing it?
I can't back this up with any evidence, but I think the reason it doesn't work well is that at the temperature required to caramelize sugar, the other "impurities" in brown sugar will be burned and gross. You might be able to get a similar effect by making regular white-sugar caramel and then mixing in molasses after it has begun to cool.