Thoroughly wash sorrel leaves and slice them.
Bring about 2l of water to boil. Add the potatoes and simmer for 7-8 minutes.
In the meantime, stir-fry onions and carrots over medium-high heat in a mix of oil and butter until the onions turn golden brown.
Add the carrot and onion mixture to the pot with potatoes. Season with salt and simmer for another 2-3 minutes or until the potatoes are cooked.
Add sorrel to the pot and mix well.
Slowly pour the beaten egg into the simmering broth, whisking as you pour. Keep whisking for another 10-20 seconds until the egg breaks into thinner ribbons.
Taste and adjust for salt.
Leave to settle for 10 minutes.
Serve garnished with fresh chopped herbs such as dill, parsley and/or cilantro and seasoned with black pepper.
For a more authentic experience, try adding a tea spoon of sour cream into your bowl.