Peel the potatoes and onions in advance. To avoid crying while cutting onions, use chewing gum, and to prevent peeled potatoes from browning, place them in cold water.
Prepare the dough. Mix kefir with flour in a deep container until smooth. Add salt, soda and egg to the resulting mixture. Mix well and knead the dough. Cover the container with the dough with a dry cloth and put it in the refrigerator for 30 minutes to make it fluffy.
While the potatoes are cooking, cut the onion into small cubes. Fry it in a frying pan with vegetable oil.
Puree the boiled potatoes and then mix with the fried onions. Add salt and pepper to the finished filling to taste.
Start making dumplings. Remove the dough for kefir dumplings from the refrigerator. Roll it out into a thin layer and cut out circles (to do this, use cookie cutters or a regular cut glass). Place the filling on each circle - potatoes with fried onions. And combine the dumplings with kefir well.
Boil the resulting dumplings in boiling salted water for 2-3 minutes.
Place the dumplings on plates in portions and add country or regular high-fat sour cream to them.