In a small bowl mix all purpose flour, baking soda and water to make smooth paste. Cover it and let it ferment overnight or 8 hours.
In another bowl, mix sooji and water to make the smooth batter. Cover this one too and let it rest overnight or at least 8 hours.
Making bhatura recipe:
In a large bowl, mix all purpose flour and salt. Add overnight rested yeast mixture and sooji paste.
Start mixing and kneading the dough till you get smooth and soft dough. NO NEED to add any extra water.
Cover it with damp towel or napkin and let it rest for 15 minutes. Then again knead to smooth it out and divide into 12 equal balls and flatten between your palm.
Roll it into 5-6 inch diameter round circle of even thickness. Roll few of them and arrange them on a plate, keep them covered.
Heat the oil for deep frying on medium high heat. Once hot slide rolled one into hot oil. It will puff up like poori.
Once there is no more bubbles, flip the it using slotted spatula and fry other side. It should be light brown in color.
Remove it using slotted spoon and drain out excess oil. Remove it on paper towel lined plate