1. Stir cocoa into butter in large bowl; cool slightly. Stir in 1/2 cup flour, sugar, eggs, vanilla, baking soda and salt; beat until well blended. Stir in remaining 1/2 cup flour and pecans until blended. Cover; refrigerate until firm, about 3 hours.
2. Heat oven to 300°F. Lightly grease cookie sheet or line with parchment paper. Shape dough into 1-inch balls; roll in powdered sugar. Place balls 3-inches apart on prepared cookie sheet.
3. Bake 10 to 12 minutes until tops have crackled appearance and are set. Remove from cookie sheet to wire rack. Cool completely. Makes about 30 cookies.