"These can be as healthy as you want them, but they are to die for! If you can, I urge you to invest in a stone baking sheet, they are fabulous for making cookies. Also, take the cookies out before you think they're done; they will crisp up after they're taken out."
Beat white sugar, margarine, and brown sugar together in a bowl using an electric mixer until creamy. Add egg white and vanilla extract; mix until well blended.
Combine flour, cocoa powder, baking soda, and salt in a separate bowl. Add flour mixture to the sugar mixture gradually, using a wooden spoon to work the dough together. Stir in chocolate chips and pecans.
Drop dough by the teaspoonful onto a baking sheet. Smoosh cookies down a little and make an indentation in the middle of each one. Place a small spoonful of marshmallow cream into the indentations.
Bake in the preheated oven until golden brown, 8 to 10 minutes. Cool on the baking sheet for 1 minute; transfer to a wire rack to cool completely, about 30 minutes.