Remove the contents into a vessel and add cooking soda and mix well. The batter should be thick enough to pour in a small saucepan.
Pour a spoon of oil in a hot saucepan and pour 2 ladle full of the dosa batter into it. Hold the saucepan and turn it around so that the entire saucepan is coated with the dosa batter. Pour a tsp full of oil around the edges of the dosa and keep it covered. Take care to keep the stove on a medium flame. After a few minutes, turn the dosa. Keep it covered again. Remove when both sides are done.