Preheat oven to 300 degrees. Set out a large cookie sheet. Into a medium bowl, sift flour, 1/3 cup sugar, cocoa and salt. In a second medium bowl, cream butter and vanilla until butter is light. Add flour mixture to butter mixture in fourths beating smooth after each addition. Fold in peanuts. Drop by teaspoonfuls about 2 inches apart onto the cookie sheet. Flatten each cookie to about 1/8 inch thickness with tines of fork dipped frequently in water, form a crosswise pattern. Bake until firm to the touch, 12 to 15 minutes. Remove cookies from oven and transfer onto waxed paper, placing cookies close together. Generously add remaining 1/4 cup powdered sugar over the cookies.