Cream butter and add the 2 cups powdered sugar slowly. Sift and add cocoa powder and salt.
Add sour cream and vanilla, beat til well combined then add flour, stir in chocolate chips.
This dough is really sticky. If it's too sticky to deal with put it in the refrigerator for a bit to harden up. Anyway you do it, it's messy but sooooo worth it, you'll see! Shape into 1" balls (once again I use the 1 ounce scoop) and roll in the 1/3 cocoa powder and put on cookie sheet. Do NOT flatten them. Bake 10 minutes at 325 but start checking them at about 8 or 9 minutes. You will not think these are done when it's time to take them out of the oven but th edges will just have started to turn a bit. You don't want them to look done. Let them cool then roll in the 2/3 cup powdered sugar and roll 'em really good. I usually end up taking powdered sugar in a sifter and just sift it on them as well.
These really are good and when you put them in your mouth they just start melting right away like a truffle. Make yourself a good cup of coffee to go with a couple of these. Man alive, life don't get no better.......