In a large bowl, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Combine dry ingredients; add to the creamed mixture alternately with sour cream, beating well after each addition (dough will be sticky). Cover and refrigerate for 2 hours or until easy to handle.
On a floured surface, roll out dough to 1/4-in. thickness. Cut into desired shapes with floured cookie cutters.
Place 1 in. apart on greased baking sheets. Bake at 375° for 8-12 minutes or until lightly browned. Cool for 1-2 minutes before removing to wire racks.
For frosting, in a large bowl, beat the butter, confectioners' sugar and milk until smooth. Add food coloring if desired. Frost cookies. Yield: about 9 dozen.