Cream the butter and sugar until smooth. Add the flour, sour cream, baking soda and lemon extract and blend until smooth. Divide dough in half and place each half on a piece of wax paper. Roll each section into a 2-inch log and freeze until firm.
Preheat oven to 350°F.
Remove 1 log at a time, slice dough into 1/8-inch slices. Place on ungreased cookie sheet. Bake 12 minutes, or until edges are golden brown. Remove from oven.
Cool 1 minute. Remove from pan and cool on rack. Drizzle with icing, if desired. Store in airtight container.
