Ingredients:

• Stuffing:
  5-6 medium size potatoes
• 1lb of champignon mushrooms
• 2 onions
• Ground black pepper to taste
• Salt to taste
• Oil
• Butter
• 
  Dough:
  1.5 cups of milk
• 2 tablespoons of vegetable oil
• 1 egg
• 4 cups of all purpose flour (and more for dusting)

How to prepare, step by step:

1. Prepare ingredients:

   

2. Start off by boiling potatoes as for salad (skin on, until can be easily pierced with a knife), this step can be done in advance, also boiled potatoes leftovers can be used instead:

   

3. Now it is time to prepare dumplings dough (I recap the method here, read how to make dumplings dough with milk and egg for more details): Mix milk, salt and oil in a cooking pot; bring to boil, then add 1/2 cup of flour:
   

   

   

   

   
   

   

   

   

   
   

   

   

   

   
   
4. Warm up skillet with a bit of vegetable oil over moderate heat; peel and chop onions, add them to the skillet and cook onions they softened and began to gain color, stir from time to time:

   

5. While onions are cooking, clean mushrooms, then dice them and once onions are ready, add mushrooms to them:

   

6. Cook onions with mushrooms together until juice produced by mushrooms evaporate (continue stirring from time to time), then season with salt and ground black pepper to taste, mix and turn the heat off:

   

7. Peel skin from boiled potatoes, slice them in pieces:

   

8. Prepare potato and mushroom stuffing:
   

   

   

   

   
   
   
9. Working in batches, roll a piece of dough into thin sheet with rolling pin:

   

10. Cut dough into circles with a glass about 2.5 inches in diameter:

    

11. Remove cut off dough, you can save it for later use if needed (store in plastic wrap):

    

12. Now it is time to do most of the work – assemble dumplings:
    

    

    

    

    
    

    

    

    

    
    
    
13. Now just repeat steps from 9 to 12 for all dough and stuffing you have, you will end up with about 80 dumplings with potato and mushroom stuffing:

    

    You can cook them immediately or freeze them up for later use.
14. To cook fresh made or frozen dumplings, bring a cooking pot to boil, salt water to taste and put portion of dumplings into boiling water:

    

15. Let dumplings cook until they emerge and then cook them for 5 mins more:

    

16. Then move them to a bowl using skimmer:

    

17. Grease dumplings with butter so they don’t stick to each other:

    

18. And serve with a scoop of sour cream: