In a small bowl stir together flour and baking soda; set aside.
In a medium saucepan melt the butter then remove from heat.
To the melted butter, stir in the sugars and cocoa powder.
Stir in buttermilk (or sour milk) and vanilla to the butter/sugar mix.
Stir in the flour mixture. At this point, the dough gets really stiff so put on your muscles!
Cover and chill the dough for 1 hour.
Scoop up enough dough to round into a 2/2 inch ball, then place on a cookie sheet. Squish down ball with the palm of your hand or the bottom of a glass, covered in plastic wrap, to make flat. (About 1/2 inch thick.
-In between batches, keep the dough in the refridgerator.-
Bake for 10 minutes or until edges are set. Cool on cookie sheet for 1 minute, then transfer to a wire rack and let cool. Sprinkle very lightly with powdered sugar.
*To make 1/4 cup sour milk, pour 3/4 teaspoon lemon juice or vinegar in a 1/4 measuring cup, then fill the rest of the cup up to make a total of 1/4 cup; stir. Let mixture stand for 5 minutes before using.
Info per cookie: Calories 73, total fat (g)2, saturated fat (g)1, cholesterol (mg)6, sodium (mg)38, carbohydrate (g) 12, protein (g)1. DIABETIC EXCHANGES. Other carbohydrates (d.e.)1.