Add 1 litre of vegetable oil to a wok, heat until very hot.
In a bowl, add the sieved gram flour, garlic, ginger, chillies, salt, coriander seeds, cumin seeds, turmeric and red chilli powder, fresh coriander , kasoori methi and spinach and mix. It is important sieve the gram flour as you don't want lumpy batter.
Then add the onions and mix, then add the potatoes and mix. The potato must be finely cut to ensure that it cooks quickly when the pakoras are deep fried in the wok.
Then add the water to the mixture, to make a sticky batter. You may need more water if it looks too dry, add small splashes at a time and mix. The batter should not be too runny, it should stick to your fingers. If you do add too much water, balance out by adding more gram flour. You should taste the batter to check the salt and spice consistency is to your taste.
Check the oil in the wok is very hot before you start to fry the pakoras. Just before frying the pakoras, add the bicarbonate of soda to the batter, then start to fry immediately.
Use a spoon to add in a generous tablespoon amount of the batter and add to the oil. Turn the heat down to medium, as you need the potatoes to cook fully. Cook the pakoras for around 3-4 minutes, then flip the over to fry the other side for another 3 minutes. Use a slotted spoon to drain the oil from the pakoras before letting the pakoras drain off further on a plate.