If maple is intended to be a significant flavor in the cake (i.e. you're making a maple cake, or a maple rum cake) it's not going to be the same without it. The best substitutions would be maple syrup, or white sugar plus maple extract, so that you still get that wonderful flavor.
As for quantities, looking around online, the common recommendations for replacing 1/2 cup of maple sugar seem to be:
- 3/4 cup white sugar and 1 teaspoon maple extract; or
- 1 cup maple syrup, and reducing other liquid in the recipe by 1/4 cup.
If you can do without the maple flavor, then you could just use the 3/4 cup white sugar, but I suspect it wasn't a superfluous ingredient!
In the case of this recipe, it looks like the maple is important, but there aren't liquids to reduce. That probably means that the easiest option is the maple extract, but you could also take the recommended amount of maple syrup, and boil it down until you've lost the right amount of water. (For example, for 1 cup of maple sugar, take 2 cups maple syrup and reduce it to 1.5 cups.)
Best Answer
The Chinese eggplant will have a thinner skin, less seeds (read: less bitterness); as a result, it will have an overall more delicate flavor.
You can substitute a globe eggplant (the kind usually sold in American grocery stores) equally; just be aware you'll get extra "eggplant" flavor.
Since the recipe you're using has strong flavors already, this should not be a problem. However, if the recipe were using more delicate flavors, it would not turn out quite as the recipe author intended.