Rinse and soak the lentils for 6-7 hours or overnight. Make sure you use a large bowl to soak the lentils as they will double in size.
After the soak time is over, drain and rinse the lentils again.Add the lentils to a food processor or blender, add 2 tablespoons water, and pulse into a fine paste.

Open the blender and scrape the lentils from the sides, add another tablespoon of water, and pulse again. Do not add all the water at once; add it in batches.
Pour just enough water to grind the dal into a thick yet fine paste. The batter should be thick and of dropping consistency.
Transfer the batter to a large mixing bowl and season it with cumin seeds and salt.

Whisk the Bhalla batter for about 5-6 minutes or until it is well aerated and double in size. You can use either a hand whisk, electric whisk, or a stand mixer to aerate the batter.
Take a small portion of the batter and drop it in a glass of water. If it floats on top, you are all set, but if it sinks, then you need to whisk for a few more minutes until you attain that texture. Perform the water test again and then proceed. Just remember the batter should FLOAT in water.

FRYING VADAS
Heat oil in a pan over medium heat.Once the oil is hot, use an ice cream scoop and drop the Bhalla batter into the oil. Fry the bhallas for about 7-8 minutes over medium-high heat, turning them occasionally until they turn golden brown.

Once cooked, remove them from the heat.Set them on a paper napkin to drain. Let them cool.
SOAK DAHI BHALLAS
Add the cooled bhallas to a pan of hot water.
Cover and let them soak for about 15-20 minutes.
Bhallas will soak up the water, and double in size and become soft.

After the desired time is over, take each bhalla out of the warm water and gently press it between your plans to remove excess water. Set it on a plate. Repeat this process with all the bhallas.

Whisk chilled yogurt along with the spices until smooth. You can thin the yogurt with milk or water.
Pour yogurt into a deep dish. Add the Bhallas to the yogurt.Cover the dahi bhallas with an extra layer of yogurt.

Cover with plastic wrap and store in the refrigerator. Dahi bhalla tastes good when chilled.
Just before serving, garnish with Roasted cumin seeds,Red chili powder,dahi masala, green chutney, tamarind chutney.