Cream 1/2 cup butter and the sugar until light and fluffy. Beat in the egg, vanilla, and milk. Sift cocoa and flour. Mix into butter mixture until thoroughly blended. Chill dough until firm enough to handle (about 30 minutes). Using 2 T dough, roll a rope about 12 inches long between your hands. Shape into a pretzel as follows: Make a loop bout 1 1/2 inches in diameter by crossing the ends, leaving 1-inch tails. Flip the loop down over the crossed ends. Press firmly into place. Place pretzels on greased baking sheets. Bake at
350 degrees F. for about 10 minutes. Mak frosting in a small bowl. Mix cocoa and confectioners' sugar. Gradually stir in butter and vanilla. If frosting is too thick, thin with milk. When pretzels are cool, spread with Cocoa Frosting. Make 2 dozen.