It is one of the favorite lunch from Orissa which is also served in Lord Jaganathpuri temple as the favorite food of the gods. Dahi Pakhala is like the state food of Odisha. It is found in restaurants, in shops, in temples and houses of rich and poor alike. It is as easy to make as buttermilk and has a refreshing balance of fluids, starch, salts and probiotic culture. Based on the age of the ferment, there might be some alcohol also present but its ability to fight heat and dehydration makes it an ideal afternoon beverage.
1. take some steamed rice (leftover rice is great) 1 c up (dry rice equivalent)
2. Pour about 6 cups of water/buttermilk (goal is to completely submerge the rice.
3. for seasoning you can use some fried chilli, 1/2 teaspoon mustard oil, cumin, ginger, hing, curry leaves, coriander, citron etc. (essentially use the same seasoning as curd rice)
Keep the steam rice submerged in water for atleast one day. (if you use the sake rice koji, the fermentation will happen faster (otherwise some buttermilk and old earthen pot is what is traditionally used as a starter culture) Rice cannot be malted and is difficult for the yeast to digest. Hence Koji or lacto-fermentation is ideal to achieve the flavors needed.
After you get the right mixture of tanginess and alcohol, mash the rice in a blender to a fine cloudy consistency (filter it out if you want to)
then make a tadka of mustard oil with chilli and seasoning and add it to your brew. I would strongly advise to use some salt as well to get the right electrolyte balance needed to fight the heat waves.
PS: like most indian ferment, this is supposed to be consumed fresh. People rarely tetrapack or preserve this brew, but serving it chilled might be a good idea.