With a stand mixer or handheld, beat the soy yogurt and sugar together until well incorporated. Add the oil (or melted and cooled margarine) and vanilla, mix well. Sift flour and baking soda together and mix with the ground anise seed into the yogurt mixture. The resulting batter will be very thick, but will spread out on the iron when pressure and heat is applied. Follow instructions to bake on your pizzelle iron.