In large bowl mix butter and sugar till fluffy, add eggs and vanilla mix well. Sift together flour, cocoa, baking soda, and salt, and add to creamed mixture.
Roll dough into balls about 1 inch in diameter then roll in white sugar. Place balls on ungreased cookie sheet and bake for 8 to 10 minutes. Place unwrapped chocolate kiss in the center of each cookie while still hot. Let cool and enjoy!