Mix the potatoes and onions, salt and put in a colander or small-cell sieve. Let the liquid drain, press several times with your hands to wring as much moisture as possible. One can also wring potato mass through gauze.
In a large thick-walled pan, pour the oil – its layer should be about 1 centimeter. When the oil temperature is high enough and it starts to smoke, start moulding dranics with clean, wet hands. Put a handful of potato mixture between your palms, press and spread the pancake into the heated oil. Push on the dragons with a scapula to make them even flatter, and fry until golden brown, then turn over and fry on the other side.
Remove the dranics from the pan and lay on paper towels so they soak up excess fat. Keep baking until all the potato mass runs out. Serve the dranics by putting a spoon of sour cream on each pancake, and on top of the salmon caviar. Garnish with fresh parsley leaves.
Potatoes peel, wash and immerse in cold water for 10-15 minutes. On a mandolin grater, cut the tubers into thin, narrow strips. Squeeze excess moisture from grated potatoes with a colander, sieve or gauze. Grind onions. Whisk together the egg and milk, mix with the potatoes and onions. Season with salt.
Heat the olive oil in a frying pan over a medium heat. Spread out the potato mixture using a tablespoon, press with silicone spatula and fry for 3-4 minutes on each side, until golden. Serve with sour cream, salmon caviar and spring onions.