Preheat oven to 350 degrees F
In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs then add the vanilla
In a separate bowl, stir together the flour, cocoa, baking soda, and salt; gradually mix into the creamed mixture.
Drop dough by teaspoonfuls onto parchment lined cookie sheets
Bake 9 minutes in the preheated oven. Cookies will be soft and still look slightly doughy
Let set and cool on cookie sheet for 2 minutes then remove from sheet onto wire rack to cool completely