I might try making these cookies again with darker cocoa powder. Maybe they will turn out more bitter to balance out the sweetness. I got a request to make these cookies with organic ingredients and the only organic cocoa powder I could find wasn't so great.
Here's the recipe: Martha Stewart's Cream-Filled Chocolate Cookies. The cookies actually turned out with perfect texture for sandwich cookies. They are not as cakey as other sandwich cookie recipes and not so hard and crunchy as butter cookies. They are crisp at the edges with a bit chewy middle.
The only thing I changed in the recipe (other than reducing the sugar) was substituting vanilla bean for vanilla extract in the filling.