Where an I find the muscovado sugar

King Arthur also has it in their catalog.

I order it from Amazon, Billington's brand, 10 pounds at a time - much less expensive than buying it at WF. You can substitute regular grocery store brown sugar of course, but muscovado sugar (being a true partially-refined brown sugar, not white sugar with molasses added back in) has a deeper, more complex flavor.

Most upscale markets will carry it, but if you can't find it you can substitute brown sugar.

Whole Foods should have it