Cornstarch and Baking Soda Ornament Recipe 2 Cups Baking Soda 1 Cup Cornstarch 1 1/4 Cup Cold Water Mix cornstarch and baking soda together, add water. Cook over medium heat,stirring constantly, until it becomes the constancy of mashed potatoes. Turn into a bowl cover with a damp cloth and let cool a bit. Knead dough untill it is soft and smooth. roll out the dough and cut into stars. Let them dry a bit on a flat surface and then poke a hole in the top of the star with a pin.