Whisk together curd, besan, sliced onions, garlic, ginger, turmeric, chilly powder, coriander powder, cumin powder, salt and water.
Heat a pan and add oil. Add methi seeds, cumin and dry red chilly. Stir and add heeng. Give a quick stir and add the curd mixture. Stir continuously till it gets a boil. Now lower the heat and let it cook for half hour, keep stirring in between so that it does not stick to the bottom.
In the mean time mix together besan, salt, green chilly, turmeric, chilly powder, coriander seeds, cumin, baking powder, spinach and water to make a thick batter. Heat oil in a deep pan and add small dollops of the batter to make pakora. Cook them on slow heat till they are evenly cooked and light brown on the outside. Remove and keep aside.
Check for salt in kadi and remove it to a serving bowl. 10 minutes before serving add pakora to piping hot kadi.
In a clean pan heat desi ghee, add coriander & cumin seeds. Once they crackle turn off the heat and add chilly powder, stir and immediately add this tempering on top of the dadi pakora. Serve immediately.