Muscovado Sugar is a dark, partially refined brown sugar with sticky crystals. Muscovado can be used in any recipe that calls for brown sugar including desserts, drinks or even on hot breakfast cereal. The sugar comes in varieties to very dark to medium dark.
Look for Muscovado sugar in health food stores or in the gourmet section of a well-stocked grocery store. We've found this sugar in Whole Foods Market and sometimes at Trader Joes. Barbados sugar is very similar but has a slightly finer texture.
If you don't have muscavado sugar then here are some good substitutes with notes on how easy they may be to find: