Clean and wash the mash daal / urad daal / white lentils. Soak for at least 6 hours or overnight.
Clean and wash the moong daal / yellow lentils. Soak for at least 1 ½ - 2 hours.
Drain the water and place the two types of lentil / daal in a food processor. Add salt and cumin seeds. Add water little by little, and process till a smooth yet thick paste has formed. Be careful that the machine does not overheat.
Place the ground daal paste into a bowl, add baking soda (if using) and mix. Aerate the mixture by using a wire whisk, an electric hand beater, or your hands. This will make the batter light and fluffy and help make soft dahi baray.
Heat oil in a karahi or a large frying pan on medium heat. I prefer to use a frying pan as it is far more stable and gives me more surface area. Use a spoon to drop spoonfuls of the batter in the oil, and cook till golden brown on all sides. The oil should be on medium temperature so that the batter can crisp up from the outside, and cook through on the inside. If the batter is too thin, that maybe a case of adding too much baking soda or water. In that case, add a bit of besan (chickpea flour) to adjust the consistency.
Remove the fried baray from the oil, and let drain on a kitchen towel or strainer. The baray can be cooled, put in a ziploc bag and kept in the freezer at this stage.
Take a large bowl and fill it with warm water along with a few pinches of asafoetida / hing (optional). Put the fried baray in the water and let them soak (15 - 30 minutes) till they become soft and fluffed up. If running short on time, the baray can be added in boiling water but they may become too soft, so keep an eye on them and adjust accordingly.
Remove the baray / fritters from the water one by one, gently squeezing them between your palms to remove the excess water. Place the baray in a plate or platter if serving them separately, otherwise add them in the prepared yoghurt mixture.