Brown sugar, even commercial brown sugar, is nothing more than molasses than white sugar. You can make your own brown sugar yourself by mixing molasses with white sugar. 1 tbs of molasses to 3 tbs of white sugar is extremely dark brown sugar, while 1 tbs of molasses to 7 tbs of white sugar is fairly light.
When you consider how poorly commercial brown sugar stores, what a pain it is to measure and so on, making it ad hoc makes sense. To me anyway, I've given up buying the ready-made.
Muscovado sugar is less refined than white sugar, but not molasses. Muscovado tastes a lot like brown sugar -- so much so that there's little need to use muscavado for almost any baking purpose. Muscovado is also somewhat difficult to work with because it's so coarse, lumpy and sticky.
It's true that muscavado has more nutritional value than white sugar. But be real. Can you imagine anything more pathetic than eating sugar for vitamins and minerals.
Muscovado is hard to find and expensive.
If you want a very unrefined sugar with similar (but better) taste, far more widely available through most of the U. S. of A., and reasonably priced, try Mexican piloncillo. Tastes great, but you'll have to break it up in a food processor. Good for a lot of things, but especially fantastic in coffee and barbecue sauces.
Jaggery is another possibility.
The easiest to find is turbinado aka sugar in the raw. It's also very easy to use because it's extremely consistent and available in a variety of textures.
If you substitute anything for anything else, you'll have to taste for sweetness and adjust. None of this stuff equates exactly to the store bought browns; further, the rawer sugars can vary substantially from purchase to purchase.
Hope this helps,
BDL
