Sift the flour once and measure two and one-half cups. Resift with baking soda and salt three times. Cream the shortening well and gradually add the sugar, beating until light and fluffy. Add the eggs, one at a time, beating after each addition. Add the melted chocolate, which has been slightly cooled, and mix well. Add the dry ingredients alternately with the milk and flavoring, mixing well after the last addition only. Turn into three greased, lined, 8-inch layer cake pans and bake in a moderate oven, 350 degrees for about 25 minutes, or until done.