Soak jowar and rice in enough water for 8-10 hours.
Soak urad dal (split black gram) along with methi seeds for the same time. Make sure to soak urad dal separately.
Once the grains are soaked for about 8-10 hours, drain the water from both.
Using a blender, first, start with grinding urad dal & methi. Try not to add water. Use very little water only if needed.
Transfer this urad dal mixture to a large deep vessel.
Now, grind jowar and rice to a smooth paste. Mix this jowar batter along with urad dal batter and mix well.
Cover the vessel and keep the batter aside for fermentation.
Also, keep a wide dish underneath the vessel which helps to catch the batter if it overflows.
Keep this batter vessel in a warm place without disturbing it.
Once fermented properly, the batter will double in size and get a frothy texture.
Add salt to the batter and mix gently.
In a steamer or pressure cooker heat some water.
Take the idli plates and lightly grease them with oil.
Pour the idli batter into the mould
Place the idli moulds in a steamer and cover the lid. Let them steam for about 20 minutes.
Once Idlis are done, open the steamer and remove the idli plates.
Using a spoon or backside of a knife demould the idlis.
Jowar Idli is ready.
Serve with coconut chutney or sambar.