Vanillas kifli

3/4 c  butter; unsalted, at room
           -temperature
    1/2 c  Sugar, granulated
      2 ea Egg yolks
      1 ts vanilla
      2 c  flour, all purpose
    1/2 c  vanilla sugar;*
      2 oz chocolate, semi sweet; 60 g
 
  *vanilla sugar is available in the baking section of most supermarkets, in
  bulk food stores and baking supply stores. 1. Beat butter with sugar in a
  large mixing bowl. Beat in yolks and vanilla. Gradually beat in flour. Turn
  out onto counter and knead as you would bread until well combined. Form
  into a ball, cover with a bowl and let stand at room temperature for 2
  hours. 2. Preheat oven to 375F. To form the crescents, roll about 1 Tbsp of
  the dough in the palms of your hands. Then continue rolling to form a rope
  about 3 inches long and 1/2 inch thick. Bend rope to form crescent. Repeat
  with remaining dough, placing on ungreased cookie sheets about 1 inch
  apart. Bake on centre sheet of preheated oven for about 10 to 12 minutes.
  Cookies should be white in colour. To prevent breaking, cool on cookie
  sheets for 5 minutes. Then, while cookies are still warm, carefully roll in
  vanilla sugar. Repeat with remaining cookies. Cool cookies completely. 3.
  Meanwhile, melt chocolate in a double boiler set over simmering water. When
  cookies are cool, dip tips of each cookie in melted chocolate, then set on
  waxed paper to dry.