Dark or light brown sugar or granulated sugar with molasses or treacle can be used as substitutes for muscovado sugar. For 1 cup of dark muscovado sugar, use 1 cup granulated sugar and 2 tablespoons of molasses or treacle. For light muscovado sugar, reduce the molasses to 1 tablespoon.
Muscovado sugar is an unrefined sugar made from sugar cane. It comes in varieties from very dark to light. The main difference between muscovado sugar and granulated sugars is the moisture content. Muscovado sugar is noticeably moister, and the crystals stick together in clumps. It has a taste similar to fudge or caramel.