Add baking powder to flour and set aside. Beat eggs until very light and lemon color and thick (about 10 minutes). Add sugar and anise oil or extract, and beat for 5 more minutes. Add dry ingredients and beat for another 5 minutes. Drop by teaspoonfuls 1" apart on well greased and floured cookie sheets. Let stand, uncovered, overnight at room temperature.
In the morning, bake in a moderate oven, 350 degrees, for 15 to 20 minutes. Makes about 3 1/2 dozen. Do not double recipe. Make batches singularly. Best when made 3 to 4 weeks ahead of time to enhance flavor. Store in air tight container.