Combine vinegar and milk in small bowl, set aside. In mixing bowl combine flour, 1st measure sugar, salt and baking soda. Stir well to blend. Cut in butter until mixture resembles coarse crumbs. Add raisins, add milk mixture all at once and stir with a fork until evenly moistened. Turn on lightly floured board and knead gently about 20 times. Place dough on ungreased cookie sheet. Pat or roll out to a round 1/2 inch thick. Cut into 8 wedges, but do not separate. Brush with egg yolk and sprinkle sugar on top. Bake at 400 F for 15 minutes or until done.