Beat butter and shortening with an electric mixer on high for 30 seconds. Add sugar and lemon peel; beat until combined. Beat in milk.
Beat in as much flour as you can, stir in remaining flour. Drop dough by rounded teaspoons 2 inches apart onto ungreased cookie sheets.
Bake for about 10 minutes or till edges are lightly browned. Cool on wire racks. Frost with Lemon Cream Cheese Frosting. Store, covered, in the refrigerator.
