Preheat oven to 350 degrees F (175 degrees C).

In a medium bowl, cream together the butter and sugar. Stir in the egg and sour cream. Then stir in the baking soda and salt. Gradually add the flour until dough becomes too difficult to stir. Turn the dough out onto a floured surface and knead in flour until dough is no longer sticky.

Roll the dough out to 1/4 to 1/2 inch thickness. Cut into desired shapes with cookie cutters. Place cookies 1 1/2 inches apart on unprepared cookie sheets.

Bake for 6 to 8 minutes in the preheated oven. Cookies should be lightly browned at the edges. Remove from the baking sheets to cool on wire racks.