Rinse the urad dal well and then soak in 2 cups of water for 6 to 8 hours or overnight
Rinse the idli rice well and then soak it in 4 cups of water along with fenugreek seeds and poha for 6 to 8 hours or overnight
Drain the water out completely from the urad dal and add it to a high-speed blender. Add 1¼ cups of water and blend until the batter is smooth. Take out the batter in the Instant Pot insert or in a large stainless steel pot.
Drain the water out completely from the rice and add it to the blender. Add 1½ cups of water and blend until slightly grainy. Pour the batter over the lentils batter. Add salt and mix well. You can use a silicone spatula or mix by hand.
Place the Instant Pot insert inside of the Instant Pot casing and place a non locking glass lid over it. Press the Yogurt(normal) mode and allow it to ferment for 8 hours. Keep an eye on the batter after 6 hours or so, if it starts to rise, you make want to take out the inner pot. Depending on the temperature in your kitchen, it may take up to 12 hours for the batter to fully ferment. So after the initial 8 hours, if needed you can then select the "Yogurt" mode again and let it ferment for additional 4 hours or so. Where I live it takes about 12 to 14 hours for the batter to fully ferment.
Once fermented the batter will double up its volume and will be light and airy. It will also have a slight sour smell to it. Give a quick stir and you are ready to use it.
This recipe makes 8 cups of batter which makes 32 to 36 idlis or 16 dosa/uttapam
Make sure to use cold water when blending rice and lentils
Blend urad dal to smooth consistency while the rice should be slightly coarse
Use a non locking lid on the Instant Pot when start the fermentation process. Sometimes, over fermentation can cause the batter to overflow or can even lock the Instant Pot lid
If you do not have an Instant Pot, simply put the pot of batter covered in a warm place or inside the oven with the oven lights on
The water proportions for blending the batter is based on the exact ingredients I use. If you use different rice or use urad dal instead of the gota urad dal you may need more or less water