In a medium mixing bowl stir together the flour, baking powder, and salt; set aside.
In a large mixing bowl beat the sugar and shortening with an electric mixer until combined. Beat in the egg yolk.
Combine the sour cream, baking soda, and vanilla. Mix well. Add the sour cream mixture to the sugar mixture and beat together until combined. Add half of the flour mixture and beat until combined. Beat or stir in remaining flour mixture. Cover and chill overnight or freeze 4 to 6 hours.
On a well-floured pastry cloth, drop 2 rounded tablespoons of dough for each cookie. With your hands, roll dough into an 8x1/2-inch rope. Form the rope into a circle, placing 1 end looped under the other end. Place on an ungreased cookie sheet. Bake in a 425 degree F oven about 7 minutes or until bottoms are lightly browned. Remove cookies from cookie sheet and cool slightly on a wire rack. If desired, serve warm. Place in an airtight container and store at room temperature for up to 3 days. Makes 24 cookies.